URIs with invalid %-encoding mishandled by Windows — Mozilla

On Windows XP with Internet Explorer 7 installed several “web related” URI schemes do not launch the registered protocol-handler if the URI contains an invalid %-encoded sequence. This was initially reported by Billy Rios and Nate McFeters with additional investigation by Secunia. A patch that mitigated the known exploits was shipped with Firefox 2.0.0.6 as described at MFSA 2007-27.