This morning I got some PM's from users saying they were getting a popup asking them to download a file.
I went through the system with a fine tooth comb and did not find anything.
Then another user Cosmo_kramer alerted me about the issue and noticed that others running vBulletin with Facebook Connect enabled were also having the issue.
I have for now disabled Facebook Connect and the system has gone back to normal.
Looks like Facebook changed something on their side.
Thanks to everyone who alerted me and to Cosmo for the heads up that we were not the only one with this issue.
I went through the system with a fine tooth comb and did not find anything.
Then another user Cosmo_kramer alerted me about the issue and noticed that others running vBulletin with Facebook Connect enabled were also having the issue.
I have for now disabled Facebook Connect and the system has gone back to normal.
Looks like Facebook changed something on their side.
Thanks to everyone who alerted me and to Cosmo for the heads up that we were not the only one with this issue.