I’ve narrowed an earlier issue down to a problem with kio_http. This one is much easier to reproduce:
In a KDE session, open Konsole terminal.
In the Konsole session, type a bogus web address. E.g.: http://magoo.ca
Right click the link and select “Open Link”
In a few seconds you should get multiple notifications on the desktop and several kio_http processes spawned. This notifications keeps on arriving until a “killall kio_http” is issued.