otrs -- XSS vulnerability in Firefox and Opera

OTRS Security Advisory 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.