Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in mootools-more 1.6.0 allows a malicious user to inject properties into Object.prototype.

MooTools is a collection of JavaScript utilities for JavaScript developers. All known versions include a CSS selector parser that is vulnerable to Regular Expression Denial of Service (ReDoS). An attack requires that an attacker can inject a string into a CSS selector at runtime, which is quite common with e.g. jQuery CSS selectors. No patches are available for this issue.