Barack Obama has done it. So have Oprah Winfrey, Ronald Reagan, Malcolm of "Malcolm in the Middle" and Beyoncé.

But flashing the OK hand signal, in which the thumb and index fingers form a circle, has proved hazardous in recent weeks, with the Chicago Cubs banning a fan for making the gesture behind a black TV reporter, and Oak Park River Forest High School announcing it would reprint more than 1,700 yearbooks at a cost of almost $54,000 because some students were displaying the hand sign. A second local high school, Chicago's Walter Payton College Prep, will also be reprinting its yearbook due to photographs of students making the OK sign.

What happened to the OK sign's reputation for squeaky-clean sincerity? And how should the average person respond?

The short answer is that, starting in 2017, members of a discussion board called 4chan mounted one in a series of attempts to "troll" — or mock — liberals with a right-wing hoax, claiming that the OK sign was a symbol of white supremacy, according to Mark Pitcavage, a senior research fellow at the Anti-Defamation League. The idea was that "the libs" would take up the cry that the OK symbol was racist and, in so doing, make themselves look ridiculous.

Some news outlets took the bait, and the claim was repeated on social media, Pitcavage said. Soon more right-wing trolls joined the campaign, which was anti-liberal but not necessarily white supremacist. Then some actual white supremacists took up the OK sign, apparently still largely as a way to make fun of liberals. And finally, some white supremacists started using the sign without apparent irony, most famously the New Zealand mosque shooter, a self-described racist who killed 51 Muslim worshipers March 15.

All of which leaves the OK sign at a complicated juncture, Pitcavage said.

"I think people should be careful about when and where they decide to make that symbol, because they could be accused of doing it for white supremacist purposes," he said.

At the same time, the vast majority of Americans are using the OK sign in the traditional nonracist ways, he said. That includes the "circle game," a popular pastime among kids and teens in which an upside-down OK sign is displayed below the waist. If your friend looks at your OK sign, you get to punch him.

Played in the U.S. since at least the 1980s, the circle game got a boost from an episode of the 2000s TV show "Malcolm in the Middle." The Oak Park students who made the OK sign in their yearbook photos were reportedly playing the circle game, and the Cubs fan, who has not been named, made the upside-down OK sign.

The Oak Park students were not accused of any racist intent, but school officials said they were concerned that the signal might be hurtful to some students nonetheless. Board member Matt Baron was quoted as saying those making the sign were "a cross-section of about 50 students from throughout the entire student body, cutting across gender, race and grade."

Similarly, Walter Payton principal Tim Devine stressed in a letter sent to students, faculty and parents that he did not believe the students pictured playing the circle game in six yearbook photos intended to convey a racist message.

"Let me be clear: it is fully believed that the intent of the students in the photographs was to be playful, as the Circle Game was actively being played around many campuses this academic year, including ours," Devine wrote.

Crane Kenney, Cubs president of business operations, said that after repeated attempts to reach the Cubs fan by phone, the team sent the fan a letter notifying him he was banned indefinitely from Wrigley Field. While it appeared that the Cubs had not questioned the fan directly, Kenney told WSCR-AM sports radio that the fan's gesture was "more likely than not … a racist way of interfering with everyone's enjoyment" of the telecast.

Pitcavage said he didn't know why the Cubs fan did what he did, and he likely wouldn't have been banned if there hadn't been an outcry.

Speaking in general, Pitcavage said it's important to not leap to conclusions when someone makes the OK sign.

"You cannot assume. That's the whole problem," he said. "You absolutely cannot assume what someone is doing when they make the OK sign unless there is contextual information. If the person making the sign is a known white supremacist, then one may assume. If the person making the sign has hate symbols on their clothes, or tattoos or jewelry, perhaps one can make an assumption. But in the absence of contextual evidence, you can't assume."

In 2018, Pitcavage came to the defense of Republican operative Zina Bash, who appeared to make the OK sign while sitting behind Brett Kavanaugh during his Supreme Court confirmation hearings. Pitcavage said on Twitter, "Out of all the things you should be legitimately concerned about regarding the Senate confirmation hearings … handshakes and handsigns ought not be among them."

As for President Trump's embrace of the OK sign, Pitcavage said the president was using it long before it became controversial, and that in many cases, his supporters use it as a form of trolling or a generic gesture of support for their leader, with no apparent white supremacist undertones.

"It's very complex," he said of the use of the OK sign in America today. "And it's frustrating to me, from time to time, that despite the fact that once you look into it at any depth at all, you realize it's a really complex landscape, a lot of people are not worrying about that at all and just going full steam ahead, assuming that any use of it now is a white power symbol."