Authentication Bypass in BrowserSkill Local Daemon via WebSocket Origin Validation

Executive Summary

CVE-2026-94111 is an authentication bypass vulnerability in Tencent BrowserSkill through version 0.3.0. It involves improper validation of the origin header in the local WebSocket daemon, allowing any chrome-extension origin with 32 characters in the range a-p to bypass authentication. Attackers can exploit this by registering a malicious browser extension to intercept and manipulate page content, DOM, and screenshots sent to the AI agent.

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Detection Guidance

To detect this vulnerability, check if BrowserSkill is running on port 52800 using netstat or ss commands. Look for WebSocket connections with chrome-extension origins containing 32 characters in the range a-p. Inspect BrowserSkill logs for unauthorized extension connections or unexpected WebSocket handshakes.

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Impact Analysis

This vulnerability allows attackers to fully control your browser session if they trick you into installing a malicious extension. They can read pages, take screenshots, fill forms, interact with authenticated sessions, and manipulate content without your knowledge or interaction. The default port 52800 and lack of additional authentication worsen the risk.

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Compliance Impact

This vulnerability could potentially violate compliance with GDPR and HIPAA by enabling unauthorized access to sensitive user data such as page content, DOM elements, and screenshots. The lack of proper origin validation allows attackers to intercept and manipulate this data without user interaction, which may constitute a breach of confidentiality and integrity requirements under these regulations.

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Mitigation Strategies

Immediately update BrowserSkill to the latest version beyond 0.3.0. Disable the local WebSocket daemon if not required. Block port 52800 at the firewall level. Remove any untrusted browser extensions and monitor for suspicious activity in browser sessions.

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