jQuery before 3.4.0 as used in Drupal Backdrop CMS and other products mishandles jQuery.extend(true {} ...) because of Object.prototype pollution. If an unsanitized source object contained an enumerable __proto__ property it could extend the native Object.prototype.

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CVE-2019-11358

CVE-2019-11358 is a prototype pollution vulnerability in jQuery (before 3.4.0) where mishandling of extend(true, {}, ...) can extend Object.prototype if an unsanitized source object has an enumerable proto property. The Core issue is triggered when a polluted prototype is introduced via nested ob...