Hi, there is a security bug open (#854739) and I'll try to port a simple patch from slixmpp. (Or, if does not work, just remove the affected functionality - better no carbons than "dangerous" ones.)
But the package will be removed from testing by overmorrow. What do I have to do so that sleekxmpp remains in stretch (or can get back to it)? I was in VAC etc. (mainly "etc.") and couldn't react earlier. TIA!