TYPO3 Core

This is something that has been bugging me for some time now:

When I open an empty sys_template in the backend and try to paste something into either constants or setup, a Javascript error triggers in CodeMirror's undo.js, which incidentially aborts the paste action. The weird thing is that this behavior is not consistent. Sometimes the content is pasted completely, sometimes only the first line. Most of the time nothing is pasted.

This only happens in Firefox (afaik), and only if the editor window is completely empty. It also happens in other instances of the t3editor/CodeMirror within the Backend (not just sys_template). I observed this behavior as far back as TYPO3 4.5, and with many different Firefox versions and installations.