Secunia Research has discovered two vulnerabilities in Mozilla Firefox, which can be exploited by malicious people to spoof file types in the file download dialog.
1) The filename and the "Content-Type" header are not sufficiently validated before being displayed in the file download dialog. This can be exploited to spoof file types in the file download dialog by sending specially crafted headers containing white spaces, dots, and ASCII bytes 160.
Successful exploitation may trick a user into executing malware if the file is opened through the file download dialog.
The vulnerability has been confirmed in Mozilla Firefox 0.10.1 for Windows. Other versions may also be affected.
2) The "Content-Type" header is used for associating a file to a file type in the file download dialog, but the file extension is left intact when saving the file to disk with "Save to Disk". This can be exploited to spoof file types in the file download dialog.
Successful exploitation may result in malware being saved to the download directory, which by default is the desktop.
NOTE: If the downloaded malware is a shortcut or some executable file, then the icon can be spoofed in the download manager and on the desktop.
The vulnerability has been confirmed in Mozilla Firefox 1.0 for Windows. Other versions may also be affected.
Solution: The vulnerabilities have been partially fixed in version 1.0.1.
Provided and/or discovered by: Andreas Sandblad, Secunia Research.
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Subject: Mozilla Firefox Download Dialog Spoofing Vulnerabilities
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