Duplicate documents detection in Elasticsearch

Yes, you can detect plagiarism, at client side. Use fingerprinting method and More-like-this to detect various degrees of document similarity.

You can easily detect duplicates, by just indexing checksum, like CRC-32 or Adler.

There is no plugin I know of and the reason is obvious, the scenarios and requirements are too difficult for a generic solution. You have to program the detection for yourself.

See Plagiarism detection