Wait... are you using IE?
This is happening too often for my liking. Additionally I would like to point out that the ONLY reason you found out about the malicious plugin...
[insert sad meow sound]
I guess we will have to wait and see. No point in speculating at this time.
So much repetitive information on the forums regarding this issue. It gets a little tedious reading the same thing over and over again.
No Developer on this site will help you with this and rightly so.
For experimental purposes I changed the server jar from the latest stable craftbukkit build to FTB-Yogscraft pack, due to a number of people...
Separate names with a comma.