BREAKING NEWS: Security researchers have uncovered a dangerous vulnerability in the Comet browser developed by Perplexity, allowing hidden extensions to execute local commands on users’ devices without their knowledge. The findings, released by experts at SquareX, reveal that this flaw breaks established browser security protocols, posing an urgent risk to users worldwide.
The newly identified MCP API enables embedded extensions to run arbitrary commands, effectively bypassing essential security measures long upheld by traditional browsers. SquareX warns that any compromise of the Comet browser could lead to severe consequences, including the execution of ransomware like WannaCry, file exfiltration, or unauthorized application launches.
Researchers discovered that Comet secretly installs two hidden extensions—an analytics tool and an automation agent—without displaying them in the browser’s extensions menu. Users are unable to view, manage, or disable these extensions, even though they are granted elevated privileges through the undocumented API call chrome.perplexity.mcp.addStdioServer. This lack of transparency means users have no way of knowing that their browser is capable of executing local commands.
The implications of this vulnerability are staggering. SquareX demonstrated how attackers could exploit the MCP API using a proof-of-concept attack. By creating a spoofed extension that mimics Comet’s legitimate extensions, attackers can sideload malicious code, leading to script injections that execute commands directly on the user’s device. This flaw essentially removes the core isolation layer that protects modern browsers, exposing users to unprecedented risks.
While SquareX has found no evidence that Perplexity has exploited this API maliciously, the presence of these hidden extensions poses a significant third-party risk for organizations. Security teams are urged to take immediate action to protect their environments.
Experts recommend blocking or restricting the use of the Comet browser until Perplexity provides comprehensive advisories and fixes. Organizations should enforce strict application control policies to prevent unauthorized browser installations and extensions. Regular audits of endpoints and monitoring of EDR logs for unusual activities are essential to ensure security.
As the landscape of AI-driven browsers evolves, this incident underscores the pressing need for heightened vigilance. Many AI-enhanced browsers may introduce features that compromise existing security frameworks in their rush to innovate. It has become crucial for organizations to adopt a zero-trust approach, treating every browser and connection as untrusted until proven otherwise.
The rapid evolution of AI-powered tools means that security frameworks must adapt quickly to identify and mitigate hidden risks. Building cyber resilience involves anticipating that even trusted tools can introduce unforeseen vulnerabilities and preparing defenses accordingly.
Stay tuned for further updates on this developing story. Share this urgent information to ensure that others are aware of the potential risks associated with the Comet browser.
