I decided to do some research: The original developer of QLS, Martin Kooij, sold this addons code (among others) to an advertizing company around 2012/2013. Their site ppclick.com is registered anonymously with GODADDY but does not respond to my browser.
I downloaded the addon code to see whether I can find anything suspicious in it but I can't (I'm no developer anyway).
http://www.systemlookup.com/FF_Extensio ... F_xpi.html
Aggressive versions 220.127.116.11+ have been reverted, but the add-on cannot be trusted anymore.
So the code seems to be clean atm but if solydxk-adjustments keeps on using it maybe updates for that addon should be disabled by default? So that nothing beyond Version 18.104.22.168.1-signed gets installed?
Using something else would be preferable though.