Stored XSS via crafted URLs in HTML ticket content in Request Tracker

RT's automatic link creation for URLs in HTML ticket content does
not HTML-escape the URL it places in the link. A URL crafted to
break out of the link's address can add a script that runs when the
ticket history is displayed, with no further action by the viewer.
Anyone who can add HTML content to a ticket can plant it. That
includes an unauthenticated sender of HTML email to any queue that
grants CreateTicket or ReplyToTicket to Everyone, which is routine
for a queue that accepts mail from the public. The script runs in
the session of any user who views the ticket, and can act in RT
with that user's authority.

This issue was fixed in version 5.0.11 and 6.0.4