Daf Hashavua Pesachim 118a
The Rif , Rambam, etc. hold , you are supposed to drink 5 cups of wine at the Seder.
Just over 100 years ago there was a *Rov who claimed to have acquired a manuscript, found in the *Royal Library in Metz.
The manuscript was from the Maharal’s son in law, R. Eliya Katz, on the Hagadah Shel Pesach.
The manuscript contained two Pirushim, named, “Divrei Negidim and Leshon Limudim” .
Both Pirushim were (supposedly) written by R.E. Katz quoting the Maharal and his Minhagim.
Up until then, there was only a single Pirush from the Maharal called Gevuras Hashem.(original)
The Rov printed the new *Maharal Hagadah with all three Pirushim.
The truth is, the Rov invented the two Pirushim and claimed it to be authentic Toireh from the Maharal (written by R.S.K.). There are many proofs that it is a fraud.
In the Hagadah he writes, “the Maharal said, people should adopt the Minhag of having a fifth cup at the Seder and say ,Hineni Muchan Umezuman etc. and the Mahral personally,did so as well.”
a) The Maharal, most likely didn’t say “Hineni Muchan Umezuman” for any Mitzvah.
b) The Maharal writes befeirush that our Minhag is to have only four cups.
* There never was a Royal Library in Metz
*Today, all Maharal Hagados have the 3 Pirushim