Seems to be Ksenia Sobchak's watermark
Probably a dog. "sobaka" means "dog" in russian
https://www.instagram.com/xenia_sobchak/
I've clocked them at 553 posts/min (>33000 posts/hr) in bread #21203 (16820565.html)
They started spamming 21:39:58, when bread had around 20 posts, bread was full 21:41:43
but that was before per post captcha though
>How could they hack the captcha
Without hacking even, probably.
It's just money, if you have enough.