DOM Based Cross-site Scripting in rails-ujs for contenteditable HTML Elements

NOTE: rails-ujs is part of Rails/actionview since 5.1.0.

There is a potential DOM based cross-site scripting issue in rails-ujs
which leverages the Clipboard API to target HTML elements that are
assigned the contenteditable attribute. This has the potential to
occur when pasting malicious HTML content from the clipboard that
includes a data-method, data-remote or data-disable-with attribute.

This vulnerability has been assigned the CVE identifier CVE-2023-23913.

Not affected: < 5.1.0
Versions Affected: >= 5.1.0
Fixed Versions: 6.1.7.3, 7.0.4.3

Impact
If the specified malicious HTML clipboard content is provided to a
contenteditable element, this could result in the arbitrary execution
of javascript on the origin in question.

Releases
The FIXED releases are available at the normal locations.

Workarounds
We recommend that all users upgrade to one of the FIXED versions.
In the meantime, users can attempt to mitigate this vulnerability
by removing the contenteditable attribute from elements in pages
that rails-ujs will interact with.

Patches
To aid users who aren’t able to upgrade immediately we have provided
patches for the two supported release series. They are in git-am
format and consist of a single changeset.

• rails-ujs-data-method-contenteditable-6-1.patch - Patch for 6.1 series
• rails-ujs-data-method-contenteditable-7-0.patch - Patch for 7.0 series

Please note that only the 7.0.Z and 6.1.Z series are
supported at present, and 6.0.Z for severe vulnerabilities.

Users of earlier unsupported releases are advised to upgrade as
soon as possible as we cannot guarantee the continued availability
of security fixes for unsupported releases.

Credits
We would like to thank ryotak 15 for reporting this!

• rails-ujs-data-method-contenteditable-6-1.patch (8.5 KB)
• rails-ujs-data-method-contenteditable-7-0.patch (8.5 KB)
• rails-ujs-data-method-contenteditable-main.patch (8.9 KB)