diff --git a/ext/bs4/__init__.py b/ext/bs4/__init__.py
index 3d2ab09aac..d8ad5e1dc1 100644
--- a/ext/bs4/__init__.py
+++ b/ext/bs4/__init__.py
@@ -15,8 +15,8 @@
 """
 
 __author__ = "Leonard Richardson (leonardr@segfault.org)"
-__version__ = "4.12.2"
-__copyright__ = "Copyright (c) 2004-2023 Leonard Richardson"
+__version__ = "4.12.3"
+__copyright__ = "Copyright (c) 2004-2024 Leonard Richardson"
 # Use of this source code is governed by the MIT license.
 __license__ = "MIT"
 
diff --git a/ext/bs4/builder/__init__.py b/ext/bs4/builder/__init__.py
index 2e3974587e..ffb31fc25e 100644
--- a/ext/bs4/builder/__init__.py
+++ b/ext/bs4/builder/__init__.py
@@ -514,15 +514,19 @@ class DetectsXMLParsedAsHTML(object):
     XML_PREFIX_B = b'<?xml'
     
     @classmethod
-    def warn_if_markup_looks_like_xml(cls, markup):
+    def warn_if_markup_looks_like_xml(cls, markup, stacklevel=3):
         """Perform a check on some markup to see if it looks like XML
         that's not XHTML. If so, issue a warning.
 
         This is much less reliable than doing the check while parsing,
         but some of the tree builders can't do that.
 
+        :param stacklevel: The stacklevel of the code calling this
+        function.
+
         :return: True if the markup looks like non-XHTML XML, False
         otherwise.
+
         """
         if isinstance(markup, bytes):
             prefix = cls.XML_PREFIX_B
@@ -535,15 +539,16 @@ def warn_if_markup_looks_like_xml(cls, markup):
             and markup.startswith(prefix)
             and not looks_like_html.search(markup[:500])
         ):
-            cls._warn()
+            cls._warn(stacklevel=stacklevel+2)
             return True
         return False
 
     @classmethod
-    def _warn(cls):
+    def _warn(cls, stacklevel=5):
         """Issue a warning about XML being parsed as HTML."""
         warnings.warn(
-            XMLParsedAsHTMLWarning.MESSAGE, XMLParsedAsHTMLWarning
+            XMLParsedAsHTMLWarning.MESSAGE, XMLParsedAsHTMLWarning,
+            stacklevel=stacklevel
         )
         
     def _initialize_xml_detector(self):
diff --git a/ext/bs4/builder/_html5lib.py b/ext/bs4/builder/_html5lib.py
index dac2173214..7c46a85118 100644
--- a/ext/bs4/builder/_html5lib.py
+++ b/ext/bs4/builder/_html5lib.py
@@ -77,7 +77,9 @@ def prepare_markup(self, markup, user_specified_encoding,
 
         # html5lib only parses HTML, so if it's given XML that's worth
         # noting.
-        DetectsXMLParsedAsHTML.warn_if_markup_looks_like_xml(markup)
+        DetectsXMLParsedAsHTML.warn_if_markup_looks_like_xml(
+            markup, stacklevel=3
+        )
 
         yield (markup, None, None, False)
 
diff --git a/ext/bs4/builder/_htmlparser.py b/ext/bs4/builder/_htmlparser.py
index e065096bd4..3cc187f892 100644
--- a/ext/bs4/builder/_htmlparser.py
+++ b/ext/bs4/builder/_htmlparser.py
@@ -378,10 +378,10 @@ def feed(self, markup):
         parser.soup = self.soup
         try:
             parser.feed(markup)
+            parser.close()
         except AssertionError as e:
             # html.parser raises AssertionError in rare cases to
             # indicate a fatal problem with the markup, especially
             # when there's an error in the doctype declaration.
             raise ParserRejectedMarkup(e)
-        parser.close()
         parser.already_closed_empty_element = []
diff --git a/ext/bs4/builder/_lxml.py b/ext/bs4/builder/_lxml.py
index 971c81e56f..4f7cf74681 100644
--- a/ext/bs4/builder/_lxml.py
+++ b/ext/bs4/builder/_lxml.py
@@ -179,7 +179,9 @@ def prepare_markup(self, markup, user_specified_encoding=None,
             self.processing_instruction_class = ProcessingInstruction
             # We're in HTML mode, so if we're given XML, that's worth
             # noting.
-            DetectsXMLParsedAsHTML.warn_if_markup_looks_like_xml(markup)
+            DetectsXMLParsedAsHTML.warn_if_markup_looks_like_xml(
+                markup, stacklevel=3
+            )
         else:
             self.processing_instruction_class = XMLProcessingInstruction
 
diff --git a/ext/bs4/element.py b/ext/bs4/element.py
index 9c73957c3f..0aefe734b2 100644
--- a/ext/bs4/element.py
+++ b/ext/bs4/element.py
@@ -1356,7 +1356,7 @@ def _clone(self):
         This is the first step in the deepcopy process.
         """
         clone = type(self)(
-            None, self.builder, self.name, self.namespace,
+            None, None, self.name, self.namespace,
             self.prefix, self.attrs, is_xml=self._is_xml,
             sourceline=self.sourceline, sourcepos=self.sourcepos,
             can_be_empty_element=self.can_be_empty_element,
@@ -1845,6 +1845,11 @@ def _indent_string(self, s, indent_level, formatter,
         return space_before + s + space_after
 
     def _format_tag(self, eventual_encoding, formatter, opening):
+        if self.hidden:
+            # A hidden tag is invisible, although its contents
+            # are visible.
+            return ''
+
         # A tag starts with the < character (see below).
 
         # Then the / character, if this is a closing tag.
diff --git a/ext/bs4/formatter.py b/ext/bs4/formatter.py
index c821318d9b..9fa1b57cb6 100644
--- a/ext/bs4/formatter.py
+++ b/ext/bs4/formatter.py
@@ -51,7 +51,7 @@ def __init__(
             void_element_close_prefix='/', cdata_containing_tags=None,
             empty_attributes_are_booleans=False, indent=1,
     ):
-        """Constructor.
+        r"""Constructor.
 
         :param language: This should be Formatter.XML if you are formatting
            XML markup and Formatter.HTML if you are formatting HTML markup.
@@ -76,7 +76,7 @@ def __init__(
             negative, or "" will only insert newlines. Using a
             positive integer indent indents that many spaces per
             level. If indent is a string (such as "\t"), that string
-            is used to indent each level. The default behavior to
+            is used to indent each level. The default behavior is to
             indent one space per level.
         """
         self.language = language
diff --git a/ext/bs4/tests/__init__.py b/ext/bs4/tests/__init__.py
index dbb1593e25..325affefcd 100644
--- a/ext/bs4/tests/__init__.py
+++ b/ext/bs4/tests/__init__.py
@@ -1105,7 +1105,7 @@ def test_find_by_prefixed_name(self):
         doc = """<?xml version="1.0" encoding="utf-8"?>
 <Document xmlns="http://example.com/ns0"
     xmlns:ns1="http://example.com/ns1"
-    xmlns:ns2="http://example.com/ns2"
+    xmlns:ns2="http://example.com/ns2">
     <ns1:tag>foo</ns1:tag>
     <ns1:tag>bar</ns1:tag>
     <ns2:tag key="value">baz</ns2:tag>
diff --git a/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-4670634698080256.testcase b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-4670634698080256.testcase
new file mode 100644
index 0000000000..4828f8a423
--- /dev/null
+++ b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-4670634698080256.testcase
@@ -0,0 +1 @@
+ ÿÿ      ÿ <css
\ No newline at end of file
diff --git a/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5000587759190016.testcase b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5000587759190016.testcase
new file mode 100644
index 0000000000..8a585ce927
Binary files /dev/null and b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5000587759190016.testcase differ
diff --git a/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5270998950477824.testcase b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5270998950477824.testcase
new file mode 100644
index 0000000000..fd411427d7
Binary files /dev/null and b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5270998950477824.testcase differ
diff --git a/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5375146639360000.testcase b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5375146639360000.testcase
new file mode 100644
index 0000000000..6248b2c54f
--- /dev/null
+++ b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5375146639360000.testcase
@@ -0,0 +1 @@
+ÿ                 ><applet></applet><applet></applet><apple|><applet><applet><appl›„><applet><applet></applet></applet></applet></applet><applet></applet><apple>t<applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet>et><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><azplet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><plet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet><applet></applet></applet></applet></applet></appt></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet></applet><<meta charset=utf-8>
\ No newline at end of file
diff --git a/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5492400320282624.testcase b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5492400320282624.testcase
new file mode 100644
index 0000000000..107da539fc
Binary files /dev/null and b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-5492400320282624.testcase differ
diff --git a/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-6306874195312640.testcase b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-6306874195312640.testcase
new file mode 100644
index 0000000000..b60a250cad
--- /dev/null
+++ b/ext/bs4/tests/fuzz/clusterfuzz-testcase-minimized-bs4_fuzzer-6306874195312640.testcase
@@ -0,0 +1 @@
+-      ÿÿ  <math><select><mi><select><select>t
\ No newline at end of file
diff --git a/ext/bs4/tests/fuzz/crash-ffbdfa8a2b26f13537b68d3794b0478a4090ee4a.testcase b/ext/bs4/tests/fuzz/crash-ffbdfa8a2b26f13537b68d3794b0478a4090ee4a.testcase
new file mode 100644
index 0000000000..8857115540
Binary files /dev/null and b/ext/bs4/tests/fuzz/crash-ffbdfa8a2b26f13537b68d3794b0478a4090ee4a.testcase differ
diff --git a/ext/bs4/tests/test_fuzz.py b/ext/bs4/tests/test_fuzz.py
index f778539a84..f29802d420 100644
--- a/ext/bs4/tests/test_fuzz.py
+++ b/ext/bs4/tests/test_fuzz.py
@@ -14,30 +14,75 @@
     BeautifulSoup,
     ParserRejectedMarkup,
 )
+try:
+    from soupsieve.util import SelectorSyntaxError
+    import lxml
+    import html5lib
+    fully_fuzzable = True
+except ImportError:
+    fully_fuzzable = False
+    
 
+@pytest.mark.skipif(not fully_fuzzable, reason="Prerequisites for fuzz tests are not installed.")
 class TestFuzz(object):
 
     # Test case markup files from fuzzers are given this extension so
     # they can be included in builds.
     TESTCASE_SUFFIX = ".testcase"
 
+    # Copied 20230512 from
+    # https://github.com/google/oss-fuzz/blob/4ac6a645a197a695fe76532251feb5067076b3f3/projects/bs4/bs4_fuzzer.py
+    #
+    # Copying the code lets us precisely duplicate the behavior of
+    # oss-fuzz.  The downside is that this code changes over time, so
+    # multiple copies of the code must be kept around to run against
+    # older tests. I'm not sure what to do about this, but I may
+    # retire old tests after a time.
+    def fuzz_test_with_css(self, filename):
+        data = self.__markup(filename)
+        parsers = ['lxml-xml', 'html5lib', 'html.parser', 'lxml']
+        try:
+            idx = int(data[0]) % len(parsers)
+        except ValueError:
+            return
+
+        css_selector, data = data[1:10], data[10:]
+
+        try:
+            soup = BeautifulSoup(data[1:], features=parsers[idx])
+        except ParserRejectedMarkup:
+            return
+        except ValueError:
+            return
+
+        list(soup.find_all(True))
+        try:
+            soup.css.select(css_selector.decode('utf-8', 'replace'))
+        except SelectorSyntaxError:
+            return
+        soup.prettify()
+    
     # This class of error has been fixed by catching a less helpful
     # exception from html.parser and raising ParserRejectedMarkup
     # instead.
     @pytest.mark.parametrize(
         "filename", [
             "clusterfuzz-testcase-minimized-bs4_fuzzer-5703933063462912",
+            "crash-ffbdfa8a2b26f13537b68d3794b0478a4090ee4a",
         ]
     )
     def test_rejected_markup(self, filename):
         markup = self.__markup(filename)
         with pytest.raises(ParserRejectedMarkup):
             BeautifulSoup(markup, 'html.parser')
-
+            
     # This class of error has to do with very deeply nested documents
     # which overflow the Python call stack when the tree is converted
     # to a string. This is an issue with Beautiful Soup which was fixed
     # as part of [bug=1471755].
+    #
+    # These test cases are in the older format that doesn't specify
+    # which parser to use or give a CSS selector.
     @pytest.mark.parametrize(
         "filename", [
             "clusterfuzz-testcase-minimized-bs4_fuzzer-5984173902397440",
@@ -46,18 +91,44 @@ def test_rejected_markup(self, filename):
             "clusterfuzz-testcase-minimized-bs4_fuzzer-6450958476902400",
         ]
     )
-    def test_deeply_nested_document(self, filename):
+    def test_deeply_nested_document_without_css(self, filename):
         # Parsing the document and encoding it back to a string is
         # sufficient to demonstrate that the overflow problem has
         # been fixed.
         markup = self.__markup(filename)
         BeautifulSoup(markup, 'html.parser').encode()
 
+    # This class of error has to do with very deeply nested documents
+    # which overflow the Python call stack when the tree is converted
+    # to a string. This is an issue with Beautiful Soup which was fixed
+    # as part of [bug=1471755].
+    @pytest.mark.parametrize(
+        "filename", [
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5000587759190016",
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5375146639360000",
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5492400320282624",
+        ]
+    )
+    def test_deeply_nested_document(self, filename): 
+       self.fuzz_test_with_css(filename)
+        
+    @pytest.mark.parametrize(
+        "filename", [
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-4670634698080256",
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-5270998950477824",
+        ]
+    )
+    def test_soupsieve_errors(self, filename):
+        self.fuzz_test_with_css(filename)
+        
     # This class of error represents problems with html5lib's parser,
     # not Beautiful Soup. I use
     # https://github.com/html5lib/html5lib-python/issues/568 to notify
     # the html5lib developers of these issues.
-    @pytest.mark.skip("html5lib problems")
+    #
+    # These test cases are in the older format that doesn't specify
+    # which parser to use or give a CSS selector.
+    @pytest.mark.skip(reason="html5lib-specific problems")
     @pytest.mark.parametrize(
         "filename", [
             # b"""ÿ<!DOCTyPEV PUBLIC'''�'"""
@@ -68,7 +139,7 @@ def test_deeply_nested_document(self, filename):
 
             # b'-<math><sElect><mi><sElect><sElect>'
             "clusterfuzz-testcase-minimized-bs4_fuzzer-5843991618256896",
-
+           
             # b'ñ<table><svg><html>'
             "clusterfuzz-testcase-minimized-bs4_fuzzer-6241471367348224",
 
@@ -79,10 +150,24 @@ def test_deeply_nested_document(self, filename):
             "crash-0d306a50c8ed8bcd0785b67000fcd5dea1d33f08"
         ]
     )
-    def test_html5lib_parse_errors(self, filename):
+    def test_html5lib_parse_errors_without_css(self, filename):
         markup = self.__markup(filename)
         print(BeautifulSoup(markup, 'html5lib').encode())
 
+    # This class of error represents problems with html5lib's parser,
+    # not Beautiful Soup. I use
+    # https://github.com/html5lib/html5lib-python/issues/568 to notify
+    # the html5lib developers of these issues.
+    @pytest.mark.skip(reason="html5lib-specific problems")
+    @pytest.mark.parametrize(
+        "filename", [
+            # b'-      \xff\xff  <math>\x10<select><mi><select><select>t'
+            "clusterfuzz-testcase-minimized-bs4_fuzzer-6306874195312640",
+        ]
+    )
+    def test_html5lib_parse_errors(self, filename):
+        self.fuzz_test_with_css(filename)
+        
     def __markup(self, filename):
         if not filename.endswith(self.TESTCASE_SUFFIX):
             filename += self.TESTCASE_SUFFIX
diff --git a/ext/bs4/tests/test_tag.py b/ext/bs4/tests/test_tag.py
index 88cc202d70..c48f334567 100644
--- a/ext/bs4/tests/test_tag.py
+++ b/ext/bs4/tests/test_tag.py
@@ -219,3 +219,16 @@ def test_customization(self):
         )
         assert soup.a['class'] == 'foo'
         assert soup.a['id'] == ['bar']
+
+    def test_hidden_tag_is_invisible(self):
+        # Setting .hidden on a tag makes it invisible in output, but
+        # leaves its contents visible.
+        #
+        # This is not a documented or supported feature of Beautiful
+        # Soup (e.g. NavigableString doesn't support .hidden even
+        # though it could), but some people use it and it's not
+        # hurting anything to verify that it keeps working.
+        #
+        soup = self.soup('<div id="1"><span id="2">a string</span></div>')
+        soup.span.hidden = True
+        assert '<div id="1">a string</div>' == str(soup.div)
diff --git a/ext/readme.md b/ext/readme.md
index 68f8cafe0a..650601f1b8 100644
--- a/ext/readme.md
+++ b/ext/readme.md
@@ -5,7 +5,7 @@ ext | **`adba`** | pymedusa/[37b0c74](https://github.com/pymedusa/adba/tree/37b0
 ext | `appdirs` | [1.4.3](https://pypi.org/project/appdirs/1.4.3/) | `simpleanidb`, `subliminal` (cli only) | File: `appdirs.py`
 ext | `attrs` | [18.2.0](https://pypi.org/project/attrs/18.2.0/) | `imdbpie` | Module: `attr`
 ext | **`babelfish`** | [0.6.0](https://pypi.org/project/babelfish/0.6.0/) | **`medusa`**, `guessit`, `knowit`, `subliminal` | -
-ext | `beautifulsoup4` | [4.12.2](https://pypi.org/project/beautifulsoup4/4.12.2/) | **`medusa`**, `subliminal` | Module: `bs4`
+ext | `beautifulsoup4` | [4.12.3](https://pypi.org/project/beautifulsoup4/4.12.3/) | **`medusa`**, `subliminal` | Module: `bs4`
 ext | `bencode.py` | [4.0.0](https://pypi.org/project/bencode.py/4.0.0/) | **`medusa`** | Modules: `bencodepy`, `bencode`<br>Monkey-patched, see `medusa/init/__init__.py`
 ext | **`boto`** | [2.48.0](https://pypi.org/project/boto/2.48.0/) | `imdbpie` | -
 ext | `CacheControl` | [0.13.1](https://pypi.org/project/CacheControl/0.13.1/) | **`medusa`** | Module: `cachecontrol`
diff --git a/requirements.txt b/requirements.txt
index 2d2fe4fab9..4217d7a745 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
 adba @ https://codeload.github.com/pymedusa/adba/tar.gz/37b0c74e76b40b3dbde29e71da75a1808eb121de
 babelfish==0.6.0
-beautifulsoup4==4.12.2
+beautifulsoup4==4.12.3
 bencode.py==4.0.0
 CacheControl==0.13.1
 certifi==2023.7.22