Breaking: #73044 - JSON for ClickMenu in Backend

See Issue #73044

Description

The ClickMenu in the TYPO3 Backend now uses JSON to transport data between the server and the client.

Before, a proprietary <t3ajax> syntax with XML was used to transport the contents of the ClickMenu.

Impact

Using ClickMenu to implement a custom ClickMenu JavaScript handler instead of the default ClickMenu.js could result in unexpected behaviour.

Affected Installations

Installations with extensions that use custom ClickMenu.js behaviour.

Migration

Adapt the custom code to handle JSON responses instead of XML responses.