A few years ago many of the captchas on t-mobile’s site had a massive security flaw (no idea if this is still the case). You could request the captcha image mul

A few years ago many of the captchas on t-mobile’s site had a massive security flaw (no idea if this is still the case). You could request the captcha image multiple times (using the image url) and each time the captcha would be differently generated on demand while still having the same letters/numbers. This meant you could just request the captcha a few times, put each image through an ocr reader, and see what the captcha was most commonly read as (the correct answer almost every time). I was astonished to find that a multi-billion dollar company had such a massive flaw in their captcha system. That being said these kind of errors are really far too common.