fswiki -- XSS problem in file upload form

A Secunia security advisory reports:

A vulnerability has been reported in FreeStyle Wiki and
FSWikiLite, which can be exploited by malicious people to
conduct script insertion attacks.
Input passed in uploaded attachments is not properly
sanitised before being used. This can be exploited to inject
arbitrary HTML and script code, which will be executed in a
user’s browser session in context of an affected site when
the malicious attachment is viewed.