A missing authentication flaw in the local WebSocket transport of Tencent BrowserSkill allows a local attacker to impersonate the bsk daemon. Because remoteSocket() connects to the loopback address without credentials or peer verification, an attacker can bind to the daemon’s port before it starts or after it stops and receive full control of the extension’s tool surface, including the evaluate method. This lets the attacker run arbitrary JavaScript through Chrome DevTools Protocol in any logged‑in browser tabs, potentially exfiltrating data or injecting malicious behavior.

The vulnerability affects Tencent’s BrowserSkill extension up to and including version 0.4.2. No other versions are listed as affected in the current data, but users should verify whether they run older releases.

The reported CVSS score of 7.2 indicates a high severity for an attacker who has local control. While EPSS data is unavailable, the lack of a known KEV listing suggests no large‑scale exploitation has been observed to date. The attack vector requires local access; an adversary needs to be able to bind to the loopback WebSocket port, which indicates that compromising the host machine or placing malicious code on the system is necessary. Once the attacker gains access, the daemon’s full interface is exposed, making exploitation straightforward.