source: http://www.securityfocus.com/bid/16117/info

Drupal is prone to an HTML injection vulnerability when handling URL-encoded HTML and script code in message content. This issue is due to a failure in the application to properly sanitize user-supplied input before using it in dynamically generated content.

Attacker-supplied HTML and script code would be executed in the context of the affected Web site, potentially allowing for theft of cookie-based authentication credentials. An attacker could also exploit this issue to control how the site is rendered to the user; other attacks are also possible. 

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