Possible exploit on version 2.3.3

I have version 2.3.3 of the redirection plugin and my website received some sort of a malicious intrusion where code was dropped into index files , etc. The plugin was the only plugin that had it’s directory altered and there was an update available for it, which is where I drew my conclusion from. I just wanted to put this out there in case it’s a legit threat.

http://wordpress.org/plugins/redirection/