A security issue and two vulnerabilities have been reported in Elgg, which can be exploited by malicious users to bypass certain security restrictions and by malicious people to bypass certain security restrictions and conduct cross-site scripting attacks.

1) Input passed to the "view" parameter in index.php (when "search" is set) 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.

2) An error when processing user registration requests can be exploited to bypass account validation.

3) An error when caching access permissions for a user can be exploited to gain unauthorized access to private entities.

Successful exploitation of this vulnerability requires that no plugin is enabled which calls an entity getter in its init function.

The security issue and vulnerabilities are reported in version 1.8.4. Prior versions may also be affected.

Solution
Update to version 1.8.5.

Provided and/or discovered by
1) The vendor credits Yang Dingjie, Qualys.
2) The vendor credits Paweł Sroka.
3) The vendor credits Mike Hedman.

Original Advisory
http://blog.elgg.org/pg/blog/evan/read/209/elgg-185-released

Other references
Further details available to Secunia VIM customers

Deep Links
Links available to Secunia VIM customers