TITLE:
phpBB "Referer" Header Session ID Disclosure

SECUNIA ADVISORY ID:
SA18693

VERIFY ADVISORY:
http://secunia.com/advisories/18693/

CRITICAL:
Less critical

IMPACT:
Hijacking, Cross Site Scripting, Exposure of sensitive information

WHERE:
>From remote

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

DESCRIPTION:
Maksymilian Arciemowicz has discovered a vulnerability in phpBB,
which can be exploited by malicious people to disclose sensitive
information.

The problem is that the session ID is included in the "Referer" HTTP
header when sending certain requests for external avatar images and
certain BBcode referencing external web sites. This can e.g. be
exploited to disclose the administrator's session ID by tricking the
administrator into viewing a malicious user's profile containing an
external avatar image.

This is related to:
SA16868

Successful exploitation may open up for various cross-site request
forgery and cross-site scripting attacks, but requires that support
for remote avatars is enabled (not default setting).

The vulnerability has been confirmed in version 2.0.19 and has also
been reported in prior versions.

SOLUTION:
Edit the source code to ensure that the session ID is not included in
the "Referer" HTTP header in requests for external resources.

PROVIDED AND/OR DISCOVERED BY:
Maksymilian Arciemowicz

ORIGINAL ADVISORY:
http://securityreason.com/achievement_securityalert/31

OTHER REFERENCES:
SA16868:
http://secunia.com/advisories/16868/

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