The noun kompromat denotes compromising information collected for use in blackmailing, discrediting or manipulating a person, group, etc. It also denotes a piece or a collection of such material.

For example, the following is from The great Epstein cover-up, Part 1, by the U.S. columnist Ann Coulter (born 1961), published in The Marshall News Messenger (Marshall, Texas, USA) of Wednesday 12^th January 2022—Jeffrey Epstein (1953-2019) was a U.S. financier and convicted sex offender:

It was perfectly clear—certainly by 2019—that Epstein had no legitimate source of income to fund his Caligula lifestyle, and further, that he was farming out underage girls for sex to the rich and powerful—with hidden cameras running everywhere. It sure looked like his underage sex ring was a blackmail/kompromat operation.

The English noun kompromat is a borrowing from Russian kompromat, which apparently originated in the Soviet secret-police jargon [cf. footnote], and is composed of:
– kompro-, in komprometirujuščij, meaning compromising;
– mat-, in material, meaning material.

However, in the texts containing the first two occurrences that I have found, Kompromat is—with capital initial—the name of the East-German intelligence bureau responsible for collecting compromising information:

1-: From The Art of Spying (Englewood Cliffs, N.J: Prentice-Hall, Inc., 1967), by Enrico Altavilla:

Other potential victims of blackmail are the people without nationality, 200,000 on Germany territory, and the refugees from East Germany. Every so often one of these receives a letter informing him of illness in his family; he hurries to the East only to discover that the letter was false, written at the behest of the secret service with the hope of enlisting him in their ranks. Usually this offer is made to people who have something to hide. This is why East Germans have created the “Kompromat,” the investigation bureau which delves into the private lives of the men and women whom they hope to recruit by blackmail.

2-: From W. German Master Spy Retires, by Peter Worthington, Toronto Telegram News Service, published in The Edmonton Journal (Edmonton, Alberta, Canada) of Friday 2^nd February 1968:

East German intelligence has a special bureau called Kompromat, which does nothing except delve into the social lives and backgrounds of prominent West Germans to gather blackmail material.

The earliest occurrence that I have found of kompromat in the etymological sense of compromising material is from Ease My Sorrows: A Memoir (New York: Random House, Inc., 1983), by the Soviet dissident Lev Kopelev (1912-1997), translated by Antonina W. Bouis:

Gumer told me that Shikin had been planning to take care of us for “snitching” to the Central Committee; he had already called in several zeks and free employees, started gathering a kompromat, a compromising affidavit.

The second-earliest occurrence that I have found of kompromat in the etymological sense of compromising material is from Yeltsin ¹ has taken the path toward dictatorship, by John Greer Nicholson, founding Professor of Russian and Slavic Studies at McGill University, Montreal, published in The Whig-Standard (Kingston, Ontario, Canada) of Friday 24^th September 1993:

Throughout August the Russian newspaper Izvestia, a strong Yeltsin supporter, had been announcing the probable scenario. On Aug. 6 the headline was “The President is worried by the present parliament,” on the 13^th, “The president is ready to decide personally on holding Advanced Parliamentary Elections.” On the 19^th, it was “The first salvoes in the artillery preparation. Rutskoi’s ² signature in a Swiss bank account…” On the 20^th, the headline read: “Boris Yeltsin intends to get elections in the fall.” Finally, on Sept. 2: “President temporarily removes Rutskoi.” Removing Rutskoi is comparable with Clinton’s dismissing Al Gore without impeachment.
Yeltsin had earlier promised a “battle” in September, preceded by “artillery preparation” for it in August. The Moscow prosecutor found no case against Rutskoi, and the latter plausibly asserts his signature was forged in the Swiss account. When Izvestia links the accusations against Rutskoi with the first “artillery … salvoes” it is clear that this constitutional successor and rival to Yeltsin is to be neutralized for political reasons so he cannot succeed Yeltsin if the latter is impeached.
There is a peculiar and unexplained Canadian connection between the search for forged kompromat (the Russian abbreviation for “compromising material”) on Rutskoi and the mysterious Vladimir Yakubovsky.

¹ Boris Yeltsin (1931-2007) was the President of the Russian Federation from 1991 to 1999.
² Alexander Rutskoi (born 1947) was the Vice President of the Russian Federation from 1991 to 1993. Having publicly declared his opposition to Boris Yeltsin’s economic and foreign policies, he was accused of corruption.

Note: The U.S. language columnist, linguist and lexicographer Ben Zimmer (born 1971) wrote the following in How ‘Kompromat’ Became a Word for Using Scandal as a Weapon, published in The Wall Street Journal (New York City, New York, USA) of 20^th January 2017:

In her book “How Russia Really Works,” Alena Ledeneva of University College London writes that “kompromat” is “derived from 1930s secret police jargon.” But it is difficult to know for sure how far back it goes, since such tactics were not talked about publicly until the “thaw” under the reign of Nikita Khrushchev in the 1950s and early 1960s.
[…]
To track down early examples of “kompromat” in Russian, I consulted with Donna Farina, an expert in Russian lexicography who teaches at New Jersey City University. She found the word first appearing in the Russian literary magazine Neva in 1962, though she notes that the writer appears to assume readers would already know the word.