Facebook asks for image verification (like asking to find all images with cat ) from users in case it detects a spam activity or something suspicious. Have you noticed this check recently and for which feature misuse, you got it. I am not able to reproduce this security check and need to test a related bug. Thanks in advance.
Happens mostly when Facebook think you're adding friends you don't actually know. I've developed a script that downloads all my friends profile images which helps immensely. This rarely happens to me though.
