Perplexity's Comet AI Browser May Have some Concerning Security Flaws Which Could Let Hacker Hijack Your Device

Why It Matters

The exploit undermines fundamental browser security models, exposing millions of users to remote code execution and ransomware risk, and could trigger widespread trust and liability issues for Perplexity and the broader AI‑browser market.

Summary

Cybersecurity firm SquareX has uncovered a critical vulnerability in Perplexity's AI‑driven Comet browser. The browser includes a hidden "MCP API" (chrome.perplexity.mcp.addStdioServer) that lets embedded extensions run arbitrary OS commands, a capability traditional browsers block. The flaw resides in the Agentic extension and can be triggered via the perplexity.ai site, meaning a single XSS, phishing breach or insider compromise could give attackers full control of any Comet user’s device, as demonstrated by a proof‑of‑concept that executed the WannaCry ransomware. SquareX has notified Perplexity and is awaiting a response.