First of all, you have to search the internet to see if the paper is plagiarized. Generally speaking, if the similarity exceeds 30%, it can be judged as plagiarism. If it is plagiarism, because your neighbor is a signed author, you must bear the responsibility. But in general, it will not involve criminal responsibility. However, if the other party reports or sues. First, your neighbor's job title is definitely gone, and you may be punished by your unit. Second, we must compensate for the losses and restore the reputation of the original author.

The key is to find out whether it is plagiarism. If not, just ignore him. If yes, confirm that the email was sent by the original author, and actively contact to understand. You may lose some money, but you won't lose your job.

Lz added: you must be responsible, because you signed it. Signature means responsibility. It's like buying a murderer to hurt others. Because it started when you bought paper, besides, buying paper itself is wrong. Using fake papers to apply for a job is alleged to be fraudulent, but because of China's national conditions, no one investigated it.