"scim-patch", a library to perform SCIM patch, prior to version 0.9.1 performs prototype pollution when applying a SCIM PATCH operation whose "value" object contains a key like ""__proto__.someProp"". After one such patch, "Object.prototype.someProp" is set process-wide, affecting every plain object in the Node process. Any service that calls "scimPatch()" on attacker-controlled JSON (i.e. any SCIM endpoint accepting "PATCH" from an external IdP) is exploitable on a stock Node runtime. Version 0.9.1 contains a patch. A workaround is available. Calling "Object.freeze(Object.prototype)" (and the same on "Array.prototype", "Function.prototype") at process startup neutralizes this class of bug — assignment to a frozen prototype becomes a silent no-op in sloppy mode or a "TypeError" in strict mode. Node's "--frozen-intrinsics" flag does this for built-ins automatically.