TITLE:
phpBB Avatar Script Insertion Vulnerability

SECUNIA ADVISORY ID:
SA17295

VERIFY ADVISORY:
http://secunia.com/advisories/17295/

CRITICAL:
Less critical

IMPACT:
Cross Site Scripting

WHERE:
>From remote

SOFTWARE:
phpBB 2.x
http://secunia.com/product/463/

DESCRIPTION:
K-Gen has discovered a vulnerability in phpBB, which can be exploited
by malicious people to conduct script insertion attacks.

The vulnerability is caused due to an input validation error in the
avatar upload handling. This can exploited to execute arbitrary HTML
and script code in a user's browser session in context of an affected
site by uploading a specially crafted valid image containing embedded
HTML and script code with an image file extension not matching the
image type (e.g. a valid GIF file with a ".jpg" file extension).

This may be related to vulnerability #2 in:
SA15845

Successful exploitation requires that the malicious avatar is
accessed directly in the Microsoft Internet Explorer browser (i.e.
not referenced via an image tag) and that the "avatar uploading"
setting is enabled (not default setting).

The vulnerability has been confirmed in version 2.0.17. Other
versions may also be affected.

SOLUTION:
Disable "avatar uploading" in the avatar settings.

PROVIDED AND/OR DISCOVERED BY:
K-Gen

OTHER REFERENCES:
SA15845:
http://secunia.com/advisories/15845/

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