Christopher Deason stumbled upon the psychological questionnaire on June 9, 2014. He was taking a lot of online surveys back then, each one earning him a few dollars. Nothing about this one, on an online job platform, struck him as “creepy or weird.’’

So at 6:37 that evening, he completed the first step of the survey: He granted access to his Facebook account.

Less than a second later, a Facebook app had harvested not only Deason’s profile data, but data from the profiles of 205 of his Facebook friends. Their names, birth dates, and location data, as well as lists of every Facebook page they had ever liked, were downloaded — without their knowledge or express consent — before Deason could read the first survey question.

The information was added to a massive database being compiled for Cambridge Analytica, the political data firm with links to President Trump’s 2016 campaign. None of the people whose data was collected knew it had happened, not even Deason. “I don’t think I would have gone forward with it if I had,’’ Deason, 27, said recently.

Deason and his Facebook friends became early entries in a database that would ultimately encompass tens of millions of Facebook profiles and is now at the center of a crisis facing the social media giant. News of Cambridge Analytica’s data collection, first reported last month by The New York Times and The Observer of London, has spurred a #DeleteFacebook movement and brought the social network under intensifying scrutiny from lawmakers.

Still, few of the roughly 214 million Americans with Facebook profiles know whether their data was among the information swept up for Cambridge Analytica. Facebook, which learned of the data misuse in December 2015, plans to begin telling affected users Monday, a day before its founder, Mark Zuckerberg, is to testify before Congress.

Records reviewed by The Times show roughly 300,000 people took the survey, but because of the access to friends’ information allowed at the time, Facebook said 87 million users could have been affected.

The Times, which has viewed a set of raw data from the profiles that Cambridge Analytica paid an academic researcher to obtain, contacted nearly two dozen affected Facebook users in recent weeks. Some were angry — one woman compared it to being robbed — while others were annoyed but unsurprised, having grown cynical about tech giants’ use of the data they collect. They are the first known affected Facebook users to be publicly identified.

“I’ve come to grips with the fact that you are the product on the Internet,’’ said Mark Snyder, 32, of Pompano Beach, Fla. He was among Deason’s friends whose data was collected.

“If you sign up for anything and it isn’t immediately obvious how they’re making money, they’re making money off of you,’’ said Snyder, who maintains computer networks for a living.

Zuckerberg has said the misuse of data represented a “breach of trust.’’

Until April 2015, Facebook allowed some app developers to collect some private information from the profiles of users who downloaded apps, and from those of their friends. Facebook has said it allowed this to help developers improve the “in-app’’ experience for users. But Facebook appears to have done little to verify how developers were using the data.

The questionnaire used to collect data for Cambridge Analytica was not actually on Facebook. It was hosted by a company called Qualtrics, which provides a platform for online surveys. It consisted of questions often used by psychology researchers to assess personality. The questionnaire took 10 to 20 minutes to complete.

When respondents authorized access to their Facebook profiles, the app performed its sole function: to take the users’ data and that of their friends.

Facebook has said that people who took the quiz were told their data would be used only for academic purposes, claiming that it and its users were misled by Cambridge Analytica and the researcher it hired, Alexander Kogan, a Russian-American academic. But the fine print may have told users their data could be used for commercial purposes, according to a draft of the survey’s terms of service.

Cambridge Analytica used the Facebook data to help build tools it claimed could identify the personalities of US voters and influence their behavior. The firm has said its psychographic modeling underpinned its work for Trump’s campaign in 2016.

Deason is keeping his account open for now because his business has its own page.

Otherwise, “I would delete Facebook,’’ he said.