Lodash versions 4.17.23 and earlier are susceptible to prototype pollution through the ` .unset` and ` .omit` functions. The initial fix did not fully address the issue, as an attacker can bypass the check by using array-wrapped path segments. This allows for the deletion of properties from built-in prototypes like Object.prototype, Number.prototype, and String.prototype. The issue allows deletion of prototype properties but does not permit overwriting their original behavior.