Moritz Naumann has discovered a vulnerability in Elgg, which can be exploited by malicious users to conduct script insertion attacks.

Input passed via the "params[twitter_username]" POST parameter to action/widgets/save is not properly sanitised before being used. This can be exploited to insert arbitrary HTML and script code, which will be executed in a user's browser session in context of an affected site if malicious data is viewed.

Successful exploitation requires the Twitter Widget plugin to be enabled (disabled by default).

The vulnerability is confirmed in versions 1.7.16 and 1.8.12 (Twitter Widget plugin version 1.7) and reported in the 1.7.x versions prior to 1.7.17 and in the 1.8.x versions prior to 1.8.13.

Solution
Update to version 1.7.17 or 1.8.13.

Provided and/or discovered by
Moritz Naumann, Naumann IT Security Consulting.

Changelog
Further details available to Secunia VIM customers

Original Advisory
Elgg:
http://blog.elgg.org/pg/blog/cash/read/223/elgg-1813-and-1717
https://github.com/Elgg/Elgg/commit/a74a88501c41e89c8bcd7fc650ae2f8cc0a5003d
https://github.com/Elgg/Elgg/commit/8d48d071b18ddb627d9e60540c9926c26109a893

Moritz Naumann:
http://www.openwall.com/lists/oss-security/2013/01/29/1

Deep Links
Links available to Secunia VIM customers