Silverstripe <= v2.3.4: XSS vulnerabilities

Silverstripe CMS, <http://silverstripe.org/>, version 2.3.4 and lower (and its unreleased 2.4 branch), is vulnerable to two Cross Site Scripting issues. 1. The comment posting mechanism of Silverstripe ('PostCommentForm') fails to properly sanitize the 'CommenterURL' parameter. This allows for persistent injection of HTML or javascript code within existing HTML tags. 2. The forum module is vulnerable to a reflective XSS issue caused by the search script failing to properly sanitize input to the 'Search' parameter. When invoking this URL: SILVERSTRIPESITE/forums/search/?Search=%22%20onmouseover=%22javascript:alert%280%29;%22 trying to reorder the search results will trigger execution of the injected javascript code.