TITLE:
phpBB "Allow HTML" Script Insertion Security Issue

SECUNIA ADVISORY ID:
SA18125

VERIFY ADVISORY:
http://secunia.com/advisories/18125/

CRITICAL:
Less critical

IMPACT:
Exposure of system information, Cross Site Scripting

WHERE:
>From remote

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

DESCRIPTION:
Maksymilian Arciemowicz has discovered a security issue in phpBB,
which can be exploited by malicious people to conduct script
insertion attacks.

Input passed in the message body when posting isn't properly
sanitised before being used. This can be exploited to inject
arbitrary JavaScript code, which will be executed in a user's browser
session in context of an affected site when the malicious post is
viewed.

Example:
<B C=">" onmouseover="[code]" X="<B "> H E L O </B>

Successful exploitation requires that "Allow HTML" is enabled (not
default setting).

It is also possible to disclose the full path to
"admin/admin_disallow.php" by accessing it directly with the
"setmodules" parameter set to "1" (requires that "register_globals"
is enabled).

The security issue has been confirmed in version 2.0.18. Other
versions may also be affected.

SOLUTION:
Set "Allow HTML" to "No".

PROVIDED AND/OR DISCOVERED BY:
Maksymilian Arciemowicz

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