Important: #68917 - Updated jQuery to 2.x¶
With the step from jQuery 1.x to 2.x support for older browsers and "dirty workarounds" have been dropped. Since TYPO3 CMS doesn't support "older" browsers (IE < 9) anymore, jQuery was updated from 1.x to 2.x. For extensions that ran fine with an up-to-date 1.x-version that shouldn't really make much difference. There might however be edge-cases where extension-authors might need to adapt their jQuery scripts for 2.x.