The phrase "until it was revealed" is correct and usable in written English.
You can use it to indicate a time frame leading up to the moment when something was disclosed or made known.
Example: "The truth remained hidden until it was revealed during the investigation."
Alternatives: "until it was disclosed" or "until it was uncovered."
Iran hid the construction of its Natanz nuclear enrichment plant — until it was revealed by a dissident group — as well as its construction of centrifuges to enrich uranium, until inspectors acting on a tip found them behind a false wall in a Tehran clock factory.
Until it was revealed she'd OD'd, then the judge and jury reassembled.
The Navajos did not learn about the meeting until it was revealed in the claims court case.
Still, despite all the avid interest, CBS managed to keep the big secret about who eventually survived the test until it was revealed last night.
It's what's thought to be the Sunken Hundred, the mythical land that lay submerged for centuries until it was revealed by a storm system in 2014.
Brady never disclosed he knew anything about the much-criticised deal until it was revealed in a Dublin newspaper two years ago.
The splices from the headlines continue until it is revealed that the vigilante Amazons and Plum's new associates may have something in common.
Now, clearly, a hack is in no position to criticise a historian or not until it is revealed that a historian once did something as vile as put a letter in JK Rowling's daughter's school bag.
Two wealthy couples, one American and one English, meet at a spa in Germany and spend several years in comfortable friendship until it is revealed that the American wife and the English husband are carrying on an affair that the English wife knows about but the American husband does not.
The Verizon commercial looks like an ad for De Beers until it is revealed that the Valentine's Day gift in question is not a diamond but a smartphone, and a woman rejects a man who gives her a phone because it is from AT&T.
(A classification accuracy of 95% seems excellent until it is revealed that 95% of the data modeled belong to a single class).
