Web Socket URL poisoning (reflected DOM-based)
Summary: PortSwigger describes reflected DOM-based WebSocket URL poisoning, where a script uses controllable data as the target URL of a WebSocket connection, letting an attacker construct a URL that makes another user's browser open a WebSocket to a server the attacker controls. The impact depends on how the application uses WebSockets: an attacker may capture sensitive data sent from the browser, or subvert application logic and deliver further client-side attacks if the application processes data read from the WebSocket server.
Key Takeaway: The exposure is the user's own browser opening a socket to an attacker-controlled endpoint, so any sensitive data the application sends over that connection goes straight to the attacker. PortSwigger notes its static analysis can flag false positives, so a finding without dynamic evidence needs code and execution-path review before you treat it as exploitable.
Read the original at PortSwigger Research ↗
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