SVG animate XSS vector

Summary: PortSwigger researcher Gareth Heyes published research on 28 January 2020 describing an XSS vector that hides a JavaScript URL inside the values attribute of the SVG animate tag, using the keyTimes and repeatCount attributes to keep the URL displayed rather than cycling past it. Heyes said the technique was aimed at confusing WAFs that look for the JavaScript protocol, and PortSwigger released an interactive lab in its Web Security Academy built around it.
Bottom line: A payload that keeps a JavaScript URL on screen through SVG animation timing is designed specifically to slip past WAFs that scan for the JavaScript protocol, so signature-based filtering may not catch it.

Read the original at PortSwigger Research ↗

Topics: Vulnerabilities & Patching
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