Firefox before 1.0.1 and Mozilla before 1.7.6 allows remote malicious web sites to spoof the extensions of files to download via the Content-Disposition header, which could be used to trick users into downloading dangerous content.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11152
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A100036
http://www.securityfocus.com/bid/12659
http://www.redhat.com/support/errata/RHSA-2005-384.html
http://www.redhat.com/support/errata/RHSA-2005-176.html
http://www.mozilla.org/security/announce/mfsa2005-22.html