I received an email from Facebook today notifying me that someone logged into my facebook account via XMPP. The message I received was “Facebook login from Rtgw_xmpp_username_password_login”. Although, I normally do log in to Facebook from Pidgin with XMPP. I’ve never received a notification before regarding it. Although this notices are normal for me, as I login from different machines occasionally, this is the first time I received one from XMPP.
After some research it does appear to be innocuous . Although I imagine that certain automated scripts might also login via XMPP as part of their testing of passwords, it appears as it is not unusual for a previously configured chat application to trigger this type of message.
This article from Facebook.com, explains it better: https://www.facebook.com/help/community/question/?id=10151104320371724