Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in jquery-plugin-query-object 2.2.3 allows a malicious user to inject properties into Object.prototype.
https://github.com/BlackFan/client-side-prototype-pollution/blob/master/pp/jquery-query-object.md
http://packetstormsecurity.com/files/166299/WordPress-Core-5.9.0-5.9.1-Cross-Site-Scripting.html