A weakness and multiple vulnerabilities have been reported in Vanilla Forums, which can be exploited by malicious people to conduct spoofing and cross-site scripting attacks.

1) Input passed via the "Target" parameter to index.php (when "p" is set to "/entry/signin") is not properly sanitised before being returned to the user. This can be exploited to execute arbitrary HTML and script code in a user's browser session in context of an affected site.

This vulnerability is confirmed in version 2.0.16.

2) Input passed via the "Target" parameter is not properly sanitised before being used. This can be exploited to redirect a user to an arbitrary website e.g. when a user clicks a specially crafted link to the affected script hosted on a trusted domain. No further information is currently available.

3) Input passed via the "p" parameter to index.php is not properly sanitised before being returned to the user. This can be exploited to execute arbitrary HTML and script code in a user's browser session in context of an affected site.

This vulnerability is confirmed in version 2.0.17.5.

4) An error exists within the cookie validation mechanism, which allows an attacker to conduct timing attacks against the application. This can be exploited to forge valid cookies. No further information is currently available.

Solution
Update to version 2.0.17.6.

Provided and/or discovered by
1, 3) Aung Khant, YGN Ethical Hacker Group
2, 4) Reported by the vendor.

Changelog
Further details available to Secunia VIM customers

Original Advisory
Vanilla Forums:
http://www.vanillaforums.org/discussion/14397/vanilla-2.0.17-released
http://www.vanillaforums.org/discussion/comment/134729/#Comment_134729

YGN Ethical Hacker Group:
http://yehg.net/lab/pr0js/advisories/[vanilla_forums-2.0.16]_cross_site_scripting
http://yehg.net/lab/pr0js/advisories/[vanilla_forums-2.0.17.5]_cross_site_scripting

Deep Links
Links available to Secunia VIM customers