Vulnerability Instance

Possible XSS Security Vulnerability in SafeBuffer#bytesplice
There is a vulnerability in ActiveSupport if the new bytesplice method is called on a SafeBuffer with untrusted user input.
This vulnerability has been assigned the CVE identifier CVE-2023-28120.

Versions Affected: All. Not affected: None Fixed Versions: 7.0.4.3, 6.1.7.3

# Impact

ActiveSupport uses the SafeBuffer string subclass to tag strings as html_safe after they have been sanitized.
When these strings are mutated, the tag is should be removed to mark them as no longer being html_safe.

Ruby 3.2 introduced a new bytesplice method which ActiveSupport does not yet understand to be a mutation.
Users on older versions of Ruby are likely unaffected.

All users running an affected release and using bytesplice should either upgrade or use one of the workarounds immediately.

# Workarounds

Avoid calling bytesplice on a SafeBuffer (html_safe) string with untrusted user input.