Anyway

If you use the Bad Behavior/Bad Beha­viour plu­gin for Word­Press, you will need to update it imme­di­ately if you don’t want to be blocked from access­ing your own site (which is rather dis­con­cert­ing). More details at Bad Beha­vior 2.0.11. Simply over­writ­ing the old files with the new should work; another option is to rename the bad-behavior-wordpress.php file to some­thing else, which will dis­able it, so you can then log in to the admin pages as usual.

Kudos to the plu­gin author (Michael Hamp­ton) for find­ing and fix­ing the prob­lem quickly!