postmessage
postMessage handlers without origin validation: zero-click cross-origin attacks via iframe.
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postMessage handlers without origin validation: zero-click cross-origin attacks via iframe.
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Intermediate level
1Advanced level
2DOM XSS — gadgets, postMessage handlers and CVE-2025-59840
DOM XSS isn't just innerHTML. Sources/sinks, gadget chains via toString(), postMessage handlers without origin checks, broken hash-based routing.
Zero-Click postMessage Origin Bypass — from the canvas to credit drain
The postMessage listener only validated a field of e.data — controlled by the attacker. e.origin was never checked. From an iframe loaded when opening a bot, messages injected as if the victim had written them.
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