typo -- Cross-Site Scripting

Typo Security Team reports:

Failing to properly encode the output, the default TYPO3
Exception Handler is susceptible to Cross-Site Scripting. We
are not aware of a possibility to exploit this vulnerability
without third party extensions being installed that put user
input in exception messages. However, it has come to our
attention that extensions using the extbase MVC framework can
be used to exploit this vulnerability if these extensions
accept objects in controller actions.