The flaw exists in the nlp.extend function of the Compromise library’s Public Root API. By injecting malicious data into the plugin argument, an attacker can add or modify properties on native JavaScript prototypes. This classic prototype‑pollution issue, classified as CWE‑1321 and CWE‑94, can alter the behavior of any code using the compromised library and may enable remote code execution if the polluted prototypes are later evaluated or executed.

All deployments of the Compromise package up through version 14.15.1 that expose the Public Root API’s extend functionality are vulnerable. The vendor’s fix is contained in the commit b4644ab7179700df0607521f61c1ee9b5f78d89d and should replace the affected releases.

The CVSS score of 5.3 indicates a moderate severity, and the EPSS score of less than 1 % suggests a low likelihood of exploitation. The vulnerability is not listed in the CISA KEV catalog. Attackers can reach the vulnerable code remotely via the public API, delivering crafted plugin payloads that pollute prototypes. Depending on how the target application utilizes the library, this could lead to privilege escalation or arbitrary code execution, but overall risk remains modest given the low exploitation probability.