otrs -- XSS vulnerability in Firefox and Opera could lead to remote code execution

The OTRS Project reports:

This advisory covers vulnerabilities discovered in the OTRS core
system. This is a variance of the XSS vulnerability, where an attacker
could send a specially prepared HTML email to OTRS which would cause
JavaScript code to be executed in your browser while displaying the
email in Firefox and Opera. In this case this is achieved with an
invalid HTML structure with nested tags.
Affected by this
vulnerability are all releases of OTRS 2.4.x up to and including
2.4.13, 3.0.x up to and including 3.0.15 and 3.1.x up to and including
3.1.9 in combination with Firefox and Opera.