Versions below 1.41 of the Claude Chrome extension have a high-risk prompt injection vulnerability and must be upgraded promptly

According to GoPlus citing a Koi report, the Claude Chrome extension under Anthropic has a high-risk prompt injection vulnerability, affecting all versions of the extension below 1.41.

Attackers can construct malicious web pages that silently load an iframe containing a cross-site scripting (XSS) vulnerability in the background, executing malicious payloads within the a-cdn.claude.ai subdomain. Since this subdomain is on the extension's trust whitelist, attackers can directly send malicious prompts to the Claude extension and execute them automatically, without requiring user authorization or any clicks, leaving the victim unaware.

This vulnerability can allow attackers to manipulate the Claude extension to read users' Google Drive documents, steal business access tokens, or export chat logs, and can take over the current browser session to perform sensitive operations like sending emails as the victim. GoPlus recommends that users immediately update the Claude extension to version 1.41 or above and remain vigilant against phishing links.