Adding XXE injection entry

WEB_SERVICE/WEB/_CRITICAL/XML_EXTERNAL_ENTITY_INJECTION/description.md

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+XXE (XML External Entity) injection is a critical security flaw that arises when an application parses XML input from untrusted sources without proper validation. Attackers exploit this vulnerability by injecting external entities into the XML data, potentially leading to unauthorized access to sensitive files or directories on the server, such as /etc/passwd. This breach can enable adversaries to extract confidential information, disrupt application functionality, or execute arbitrary code. XXE vulnerabilities commonly occur due to lax input validation and the misconfiguration of XML parsers, allowing malicious entities to manipulate XML structures.
+### Examples
+
+#### Java
+
+```java
+//Input example : 
+String xmlInput = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
+    "<!DOCTYPE foo [<!ENTITY xxe SYSTEM \"file:///etc/passwd\">]>\n" +
+    "<foo>&xxe;</foo>";
+
+DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
+DocumentBuilder builder = factory.newDocumentBuilder();
+Document doc = builder.parse(new ByteArrayInputStream(xmlInput.getBytes()));
+
+// Process the XML document
+// Access the parsed data, which could potentially include sensitive information
+```
+
+#### Javascript
+
+```javascript
+const app = require("express")();
+const libxml = require("libxmljs");
+app.post("/path", (req, res) => {
+  Element = libxml.parseXml(req.body, { noent: true });
+ // Processing the XML element
+});
+```
+
+#### Php
+
+```php
+<?php
+$xmlInput = '<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/passwd">]>
+<foo>&xxe;</foo>';
+
+$doc = new DOMDocument();
+$doc->loadXML($xmlInput);
+
+echo $doc->saveXML();
+?>
+
+```
+

WEB_SERVICE/WEB/_CRITICAL/XML_EXTERNAL_ENTITY_INJECTION/meta.json

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+{
+  "risk_rating": "critical",
+  "short_description": "The web application is susceptible to an XML External Entity (XXE) vulnerability.",
+  "references": {
+    "OWASP":"https://owasp.org/www-community/vulnerabilities/XML_External_Entity_(XXE)",
+    "Portswigger": "https://portswigger.net/web-security/xxe#what-is-xml-external-entity-injection"
+  },
+  "title": "XML External Entity (XXE) Injection",
+  "privacy_issue": false,
+  "security_issue": true,
+  "categories": {
+    "CWE_TOP_25": [
+      "CWE_611"
+    ],
+    "GDPR": [
+      "ART_25",
+      "ART_32"
+    ],
+    "PCI_STANDARDS":[
+      "REQ_6_4",
+      "REQ_6_5"
+    ]
+  }
+}

WEB_SERVICE/WEB/_CRITICAL/XML_EXTERNAL_ENTITY_INJECTION/recommendation.md

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+Virtually all XXE vulnerabilities arise because the application's XML parsing library supports potentially dangerous XML features that the application does not need or intend to use. The easiest and most effective way to prevent XXE attacks is to disable those features.
+
+Generally, it is sufficient to disable resolution of external entities and disable support for XInclude. This can usually be done via configuration options or by programmatically overriding default behavior. Consult the documentation for your XML parsing library or API for details about how to disable unnecessary capabilities.
+
+### Examples
+
+#### Java
+
+```java
+//Input example : 
+String xmlInput = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
+    "<!DOCTYPE foo [<!ENTITY xxe SYSTEM \"file:///etc/passwd\">]>\n" +
+    "<foo>&xxe;</foo>";
+
+DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
+
+// Enable secure processing mode to mitigate common XML security vulnerabilities
+factory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
+
+// Disable external DTDs and stylesheets to prevent potential XXE attacks
+factory.setAttribute(XMLConstants.ACCESS_EXTERNAL_DTD, "");
+factory.setAttribute(XMLConstants.ACCESS_EXTERNAL_STYLESHEET, "");
+
+DocumentBuilder builder = factory.newDocumentBuilder();
+Document doc = builder.parse(new ByteArrayInputStream(xmlInput.getBytes()));
+```
+#### Javascript
+
+```javascript
+const app = require("express")();
+const libxml = require("libxmljs");
+app.post("/path", (req, res) => {
+  Element = libxml.parseXml(req.body);
+ // Processing the XML element
+});
+```
+
+#### Php
+
+```php
+<?php
+$loadEntities = libxml_disable_entity_loader(true);
+
+$xmlInput = '<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE foo [<!ENTITY xxe SYSTEM "file:///etc/passwd">]>
+<foo>&xxe;</foo>';
+
+$doc = new DOMDocument();
+$doc->loadXML($xmlInput);
+
+libxml_disable_entity_loader($loadEntities);
+
+echo $doc->saveXML();
+?>
+```