DO NOT CONTACT THEM IN REPLY.
THE PM IS A SCAM.
It is a variation of the ancient Nigerian Scam. Snopes has some lovely information on it, including variants.
If you have already contacted them, please let one of the staff know. We will try to help (though we cannot guarantee anything). At the very least, you should change your bank and contact information ASAP.
The message, for reference:
Spoiler! :
Gender:
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