For a few weeks I have not been able to login into any SE site except Stackoverflow using Safari on my iPad. Every attempt to login with Facebook (as I usually do) leads to the same message:
Sorry, your request could not be completed because it looked suspicious. If you meant to perform an action ... please return to the previous page and try again.
I have tried hard to think or a worse bug and less helpful message I know but couldn't. Needless to say, the "advise" to "return to the previous page and try again" leads to a very predictable outcome :(