Offered AllowClipboard helper doesn't work with 2.0.0.x Firefox
When trying to copy some text from rtehtmlarea in Firefox, the browsers security policy by default doesn't allow it. rtehtmlarea can trigger the installation of a plugin which enables allowing this behaviour for certain domains (e.g. TYPO3 backends).
The current offered version is 0.5.3, which works only with Firefox until version 1.5.x. The "new" 0.5.5 also works with Firefox 2.0.0.x.
The add-on is on https://addons.mozilla.org/en-US/firefox/addon/852
Old version is 0.5.3. New version is 0.5.5. The default URL has to be changed in ext_conf_template.txt and ext_localconf.php
(issue imported from #M6152)