ThunderBox 0.9.1 does not support the login procedure of Fritz!OS 5.50 as described in http://www.avm.de/de/Extern/files/session_id/AVM_Technical_Note_-_Session_ID.pdf
Since I was in need of using ThunderBox, I modified the add-on in a manner that it supports ONLY this new login procedure (and not older ones). Furthermore there are no other changes yet (like choosing the box' phone book for export and import).
Changes made:
thunderbox.properties:
constant sync.unsupportedVersionMessage modified
thunderbox.js
addes function: getRequest: function( url, callback )
thunderboxCommon.js
constant modified: const THUNDERBOX_WEBCM_URL_PATTERN = "http://<<host>>:80/login_sid.lua";</host>
ThunderboxStateMachine.js
login via GET instead of POST: modified function: ThunderboxStateMachine.prototype.start
You can download this Version (CAUTION: Fritz!OS >= 5.50 ONLY!):
http://www.schniewind-it.de/dlfiles/public/DIVERSE/thunderbox-FOS-5.50@schniewind-it.de.xpi
I foudn a way to make calling also possible with newer FritzBox versions. If anybody is interested, it is attached. What still does not work for me is the password dialog. I hacked the code, so my password is hardcoded. Not really a solution, but it works for me :-p.