Typical severity: Medium. An attacker makes use of Cascading Style Sheets (CSS) injection to steal data cross domain from the victim's browser. The attack works by abusing the standards relating to loading of CSS: 1. Send cookies on any load of CSS (including cross-domain) 2. When parsing returned CSS ignore all data that does not make sense before a valid CSS descriptor is found by the CSS parser.
Design: Prior to performing CSS parsing, require the CSS to start with well-formed CSS when it is a cross-domain load and the MIME type is broken. This is a browser level fix. | Implementation: Perform proper HTML encoding and URL escaping