By Sead Fadilpašić
Publication Date: 2025-11-23 10:03:00
- SquareX accused Perplexity’s Comet browser of exposing a hidden MCP API that could enable local command execution
- Perplexity rejected the claims as “entirely false,” stressing the API requires developer mode, user consent, and manual sideloading
- SquareX countered, saying Comet was silently updated after its proof‑of‑concept, and that external researchers replicated the attack
Cybersecurity company SquareX recently accused Perplexity of keeping a major vulnerability in its AI browser, Comet – the latter has now responded, saying the research report is “entirely false” and part of a growing “fake security research” problem.
SquareX had said it found a hidden API in the Comet browser, capable of executing local commands. That API, named MCP API, allows its embedded extensions to execute arbitrary local commands on users’ devices, capabilities that traditional browsers explicitly prohibit.
SquareX said it found the API in the Agentic extension, which can be triggered by the perplexity.ai page, meaning that should anyone break into the Perplexity site, they will have access to devices of all of its users.
Perplexity’s response
For Kabilan Sakthivel, Researcher at SquareX, not adhering to strict security controls the industry evolved to, “reverses the clock on decades of browser security principles established by vendors like Chrome, Safari and Firefox.”
But Perplexity begs to differ, noting in a written response sent to TechRadar Pro by…
