It looks like a base64-encoded 20-byte value, which decodes to:

3f 4f 29 c4 8f aa ed a6 df be ad cb 23 0b 29 2d 1c bf 11 64

The length of a SHA-1 digest is 160 bits = 20 bytes. This does not at all conclusively mean this value may be a SHA-1 digest, but 160 bits is not a length of value that's customarily used for random nonces, random identifiers, and the like. I recommend you suppose it's a SHA-1 digest and work from there.

This is some binary Base64 encoded, would be my guess. This is because of the combination of characters and the = at the end.

That looks like the text left behind when I got hacked.