tor-browser

commit 6063b193214ce6c36548e0cd27ecda14fcd64ead
parent 1cc9a3f60fae799f6bf0cb6d149baa0678759029
Author: Daniel Minor <dminor@mozilla.com>
Date:   Wed,  5 Nov 2025 13:16:23 +0000

Bug 1997638 - Check mimetype essence for CSS modules; r=dom-core,smaug

In the initial implementation, I mistakenly checked the mime type, but section
13.7.3 of https://html.spec.whatwg.org/#fetch-a-single-module-script says
this should be the mime type essence.

Differential Revision: https://phabricator.services.mozilla.com/D271091

Diffstat:
M
dom/base/nsContentUtils.cpp
 | 
10
+++++++---
M
dom/base/nsContentUtils.h
 | 
4
++--
M
dom/script/ScriptLoader.cpp
 | 
2
+-

3 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
@@ -8657,9 +8657,13 @@ bool nsContentUtils::IsJsonMimeType(const nsAString& aMimeType) {
   return StringEndsWith(subtype, u"+json"_ns);
 }
 
-// https://html.spec.whatwg.org/#fetch-a-single-module-script, 7.3
-bool nsContentUtils::IsCssMimeType(const nsAString& aMimeType) {
-  return aMimeType.LowerCaseEqualsLiteral("text/css");
+// https://html.spec.whatwg.org/#fetch-a-single-module-script, 13.7.3
+bool nsContentUtils::HasCssMimeTypeEssence(const nsAString& aMimeType) {
+  nsString contentType, contentCharset;
+  if (MimeType::Parse(aMimeType, contentType, contentCharset)) {
+    return contentType.LowerCaseEqualsLiteral("text/css");
+  }
+  return false;
 }
 
 bool nsContentUtils::PrefetchPreloadEnabled(nsIDocShell* aDocShell) {
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
@@ -2744,10 +2744,10 @@ class nsContentUtils {
   static bool IsJsonMimeType(const nsAString& aMimeType);
 
   /**
-   * Returns true if the given MIME type string is a valid CSS MIME type,
+   * Returns true if the given MIME type string has a CSS MIME type essence,
    * otherwise false.
    */
-  static bool IsCssMimeType(const nsAString& aMimeType);
+  static bool HasCssMimeTypeEssence(const nsAString& aMimeType);
 
   static void SplitMimeType(const nsAString& aValue, nsString& aType,
                             nsString& aParams);
diff --git a/dom/script/ScriptLoader.cpp b/dom/script/ScriptLoader.cpp
@@ -4510,7 +4510,7 @@ static bool MimeTypeMatchesExpectedModuleType(
     case JS::ModuleType::JSON:
       return nsContentUtils::IsJsonMimeType(typeString);
     case JS::ModuleType::CSS:
-      return nsContentUtils::IsCssMimeType(typeString);
+      return nsContentUtils::HasCssMimeTypeEssence(typeString);
     case JS::ModuleType::Unknown:
     case JS::ModuleType::Bytes:
       break;