Detecting web message misconfigurations for cross-domain credential theft

Summary: PortSwigger researcher Gareth Heyes published a post on 9 November 2022 describing an update to Burp Suite's DOM Invader tool that inspects web message data and flags messages containing URL data sent to a different origin. The feature, built after reading Frans Rosén's post on exploiting OAuth flows, is enabled by turning on post message interception and clicking Detect cross-domain leaks, and it flags a test case where a URL with a GET parameter named secret set to supersecret is sent cross-domain.
Key Takeaway: Web messages never travel over the wire, so auditing them has meant manual JavaScript debugger breakpoints - and a URL token sent to the wrong origin can be lifted by embedding the page as an iframe with a message event listener.

Read the original at PortSwigger Research ↗

Topics: Vulnerabilities & Patching
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