Hello crypto anarchistI am introducing to you Bitcoin double spend service
That service can help you to check you own websites to double spend vulnerability.Youtube video
https://www.youtube.com/watch?v=r3fQIwTxvYMThis tool allows you to generate two transactions using the same Bitcoins. The first transaction will have a very low fee, and will only be accepted by a few nodes, but after some time it should make its way to the recipient. The second transaction will have a generous fee and will be broadcast more easily to many nodes. Publish the first transaction and wait for the recipient to receive the unconfirmed transaction. You can then broadcast the second transaction and it should reach miners first as long as the first transaction has not yet been confirmed.Our double spend service works two years old
Over 5000+ successfull double spendsPlease note! If you accept bitcoins without any confirmations you risk losing your moneyhttps://doublespend.online - website linkPlease dont use our service in illegal purposesIts makes to show people how to easy double spend bitcoins and improve web services accepting bitcoins.
Quoting for reference.
The entire project seems a scam attempt to me. You are teaching people how to steal others bitcoin, how to harm the bitcoin businesses.

Telegram archived:
https://archive.is/KKZL6
Site archived:
https://archive.is/38l7iIt seems you found a way to scam the scammers.
Trick here is you allow those people to import their private key in your site. Those greedy stupids will have no idea that they will eventually get scammed where they wanted to scam other people.
I will be tagging you after making this post to warn the newbies.Edit: Tagged!