Shimeon Cippah known in the Sefer Hasidim as Shimon Peter Chamor (פטר חמור) was a Tzadik according to R. Judah He-Hasid, leader of the twelfth century Hasidei Ashkenaz in Germany. Shimon authored some Yom Kippur liturgy and others while in a cave. Machzor Vitri p. 282 Mahadurah Makitzei Nirdamim warns Vechas Veshalom to anyone who says such a thing as connecting him to the "Abomination of Rome" and continues that anyone "who says so will have to bring a fat offering when Moshiach comes.”

He was the last leader of the Galilean Sanhedrin and later a Stylite around 426CE. He made an alliance with the Notzrim against Persian Judaizers who were attacking both Notzrut and Pavlut and was instrumental in establishing the Miaphysite Church. He also sent all the Galilean compositions outside of the Jerusalem Talmud to the Exilarch in Babylon where the Babylonian Talmud was being composed.

It may also be noted that

The Machzor Vitri p. 282 Mahadurah Makitzei Nirdamim says

“Some say Nishmas was authored by an "Abomination of Rome" called Shimon Peter Chamor(!) -who authored this liturgy and others while in the cave- Vechas Veshalom to say such a thing (that Peter is an Abomination of Rome), and one who says so will have to bring a fat offering when Moshiach comes”

Vetzaruch Iyun (צריך עיון), as elsewhere in Machzor Vitri it states that Shimon Kipa authored the Piyutim of Seder Avoda said on Yom Kippur.

Siddur Avodas Yisrael, in name of an old manuscript siddur from the year 1407

“I heard from Yehuda Bar Yaakov that Shimon Ben Kipa authored Nishmas until the words Mi Yidmeh Lach”

http://folkmasa.org/bet/bet001.htm

http://www.ybm.org.il/Admin/uploaddata/LessonsFiles/Pdf/4570.pdf

https://www.yutorah.org/_cdn/_shiurim/Fast%20of%20Ninth%20of%20Teves.pdf

http://chaimsimons.net/tevet9paper.pdf