Claude Extension Flaw Enabled Zero-Click XSS Prompt Injection via Any Website

Mar 26, 2026

Cybersecurity researchers have disclosed a vulnerability in Anthropic’s Claude Google Chrome Extension that could have been exploited to trigger malicious prompts simply by visiting a web page.
The flaw “allowed any website to silently inject prompts into that assistant as if the user wrote them,” Koi Security researcher Oren Yomtov said in a report shared with The Hacker News. “No clicks, no

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