mixin-deep is vulnerable to Prototype Pollution in versions before 1.3.2 and version 2.0.0. The function mixin-deep could be tricked into adding or modifying properties of Object.prototype using a constructor payload.

mixin-deep node module before 1.3.1 suffers from a Modification of Assumed-Immutable Data (MAID) vulnerability, which allows a malicious user to modify the prototype of "Object" via __proto__, causing the addition or modification of an existing property that will exist on all objects.