diff --git a/background/open_urls.ts b/background/open_urls.ts
index 441465b6e..932ac1c4b 100644
--- a/background/open_urls.ts
+++ b/background/open_urls.ts
@@ -14,7 +14,7 @@ import {
   convertToUrl_, createSearchUrl_, hasUsedKeyword_, lastUrlType_, quotedStringRe_, reformatURL_
 } from "./normalize_urls"
 import { findUrlEndingWithPunctuation_, findUrlInText_ } from "./parse_urls"
-import { safePost, showHUD, complainLimits, findCPort, isNotVomnibarPage, getCurFrames_ } from "./ports"
+import { safePost, showHUD, complainLimits, findCPort, isNotVomnibarPage, getCurFrames_, showHUDEx } from "./ports"
 import { createSimpleUrlMatcher_, matchSimply_ } from "./exclusions"
 import { trans_ } from "./i18n"
 import { makeCommand_ } from "./key_mappings"
@@ -594,6 +594,8 @@ export const openUrlWithActions = (url: Urls.Url, workType: Urls.WorkType, sed?:
     reuse = reuse !== ReuseType.newBg ? ReuseType.newFg : reuse
   }
   if (incog != null && incog !== (curIncognito_ === IncognitoType.true)) { reuse = ReuseType.newFg }
+  OnFirefox && typeof url === "string" && cPort && (<RegExpOne> /^file:|^about:(?!blank)/).test(url)
+      && options.warnFiles !== false && showHUDEx(cPort, "disabledUrlToOpen", 2, [])
   typeof url !== "string"
       ? void Promise.resolve(url).then(onEvalUrl_.bind(0, workType, options, tabs))
       : /*#__NOINLINE__*/ openShowPage(url, reuse, options) ? 0
diff --git a/i18n/en/background.json b/i18n/en/background.json
index e0b16fc41..0735bf078 100644
--- a/i18n/en/background.json
+++ b/i18n/en/background.json
@@ -9,6 +9,7 @@
   "copiedWndInfo": "(info of tabs)",
   "csCleared": "$1 content settings have been cleared",
   "delSug": "Succeed to delete a $1",
+  "disabledUrlToOpen": "Extensions can't open such URLs on Firefox",
   "discardFail": "Cannot discard the tab",
   "downloadFail": "Failed in downloading",
   "downloadTimeout": "Downloading took too long",
diff --git a/i18n/fr/background.json b/i18n/fr/background.json
index 2b02569c0..57d2adabe 100644
--- a/i18n/fr/background.json
+++ b/i18n/fr/background.json
@@ -9,6 +9,7 @@
   "copiedWndInfo": "(info des onglets)",
   "csCleared": "Les paramètres du contenu $1 ont été effacés",
   "delSug": "A réussi à supprimer un $1",
+  "disabledUrlToOpen": "Firefox n'autorise pas l'extension à ouvrir cette URL",
   "discardFail": "Ne peut pas décharger l'onglet",
   "downloadFail": "Échec du téléchargement",
   "downloadTimeout": "Le téléchargement a pris trop de temps",
diff --git a/i18n/zh/background.json b/i18n/zh/background.json
index 4bfdc79f6..7d1416284 100644
--- a/i18n/zh/background.json
+++ b/i18n/zh/background.json
@@ -10,6 +10,7 @@
   "copiedWndInfo": "（标签页信息）",
   "csCleared": "对各网站 $1 功能权限的修改已重置",
   "delSug": "成功删除所选$1",
+  "disabledUrlToOpen": "Firefox 不允许扩展打开此网址",
   "discardFail": "无法丢弃此网页",
   "downloadFail": "无法下载此对象",
   "downloadTimeout": "对象下载超时",
diff --git a/i18n/zh_TW/background.json b/i18n/zh_TW/background.json
index f52d45a0a..b6930c075 100644
--- a/i18n/zh_TW/background.json
+++ b/i18n/zh_TW/background.json
@@ -10,6 +10,7 @@
   "copiedWndInfo": "（分頁信息）",
   "csCleared": "對各網站 $1 功能權限的修改已重置",
   "delSug": "成功刪除所選$1",
+  "disabledUrlToOpen": "Firefox 不允許擴展存取此網址",
   "discardFail": "無法丟棄此網頁",
   "downloadFail": "無法下載此對象",
   "downloadTimeout": "對象下載超時",
diff --git a/typings/messages.d.ts b/typings/messages.d.ts
index b8ab24ffd..1add51bd1 100644
--- a/typings/messages.d.ts
+++ b/typings/messages.d.ts
@@ -779,6 +779,7 @@ interface OpenUrlOptions extends UserSedOptions {
       | "default"
   reuse?: UserReuseType | null
   window?: boolean | "popup" | "normal" | null
+  warnFiles?: true | false | null
 }
 
 interface OpenPageUrlOptions extends OpenUrlOptions {