UPDATE: This issue is fixed in version 188.8.131.52. Original reply follows.
This is a bug in Clippings Manager which will be fixed in an upcoming release. Workaround: right-click on the textbox and click Select All from the context menu.
Hopefully there won't be a need to disable automatic updating of Clippings now that there is a temporary workaround solution -- but if you must still do it, turn off automatic updates in Add-ons Manager in Firefox.
If you have any more questions, please post them to the AE Creations Help and Support Forum: https://groups.google.com/forum/#!categories/aecreations-help. Thanks.
The Mozilla team is rolling out a fix for Firefox which should resolve the certificate issue affecting all add-ons. See their Twitter feed for details: https://twitter.com/mozamo/status/1124627930301255680