The cobrowsing-exception-filter npm package (version 35.8.3) includes malicious code that, upon require(), loads a support script which dynamically reconstructs obfuscated endpoint hostnames controlled by attackers. It downloads opaque binary payloads to temporary directories, sets executable permissions, and runs them detached via system shells. The code uses runtime obfuscation techniques to evade static analysis and includes a rate-limiting marker and a telemetry disable flag as cover. No hash or signature verification is performed on the downloaded binaries, which are mutable and attacker-controlled. The package's declared purpose is misleading, as it contains no legitimate error-handling functionality.

This malicious package enables remote code execution on any system that installs and requires it, allowing attackers to run arbitrary binaries with the privileges of the executing user. The lack of integrity checks and use of attacker-controlled endpoints means the payload can be changed at any time, increasing the risk of persistent compromise or further malware deployment.

No official patch or remediation is currently documented. Users should immediately remove version 35.8.3 of cobrowsing-exception-filter from their projects and avoid installing this package. Investigate any systems where this package was used for signs of compromise. Use trusted package sources and verify package integrity before installation.