@jaymara/jsononifier versions 1.0.0, 1.0.1, and 1.0.2 include a hidden command execution backdoor triggered upon requiring the package. The index.js loads trigger.js, which checks environment variables and platform to avoid execution in CI, test, or Docker environments, and only activates on Windows workstations. It schedules Executer.js to decode an XOR-encoded command from payload.js and executes it with Windows process hiding enabled. The current payload launches calc.exe as a demonstration, but the encoded payload can be replaced to run arbitrary commands. This behavior is unrelated to the package's advertised JSON formatting functionality, indicating malicious intent.

The malicious code allows arbitrary command execution on Windows systems that import this package, potentially enabling attackers to run any commands with the privileges of the importing process. Although the current payload is benign (launching calc.exe), the mechanism can be modified to execute harmful commands, leading to system compromise, data theft, or further malware deployment. The code avoids execution in sandboxed or CI environments, increasing the risk of undetected exploitation on real victim machines.

No official patch or remediation is currently available. Users should immediately remove and avoid using @jaymara/jsononifier versions 1.0.0, 1.0.1, and 1.0.2. Audit dependencies for this package and replace it with a trusted alternative. Monitor for any unexpected child process executions on Windows systems that import this package. Patch status is not yet confirmed — check the vendor advisory or npm security advisories for updates.