postmessage
postMessage handlers without origin validation: zero-click cross-origin attacks via iframe.
Quick answer
What is postmessage?
postMessage handlers without origin validation: zero-click cross-origin attacks via iframe.
Articles
3
Beginner
0
Intermediate
1
Advanced
2
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.
Practice postmessage with real labs
Apply the techniques in safe environments based on real bug bounty reports.
hunters training
labs from real hacks
completions
paid out for these bugs
The checklist I run on every new target
47 checks ordered by cost: first what can get you in trouble, then the cheap stuff, and finally the expensive stuff — which is where the big bounties are. I'll send it to your inbox right now.
Unsubscribe in one click, from any email.
Stop reading about bugs and start hunting them
Create your free account and practice on labs based on real hacks that paid out thousands of euros. The Academy is free forever.
No card · free Academy · cancel anytime