Trump's Press Secretary put out a video, which appears to be edited and sped up to show a chopping motion which doesn't seem to happen in the original video. "Surely you don't trust InfoWars.?" he said on Twitter. "His statement, 'Pardon me, ma'am, ' is not included in the video Sanders shared", Washington Post technology reporter Drew Harwell wrote.
Trump responded: "CNN should be ashamed of itself having you working for them".
The heated exchange began after Acosta clung to the microphone and persisted with questions about the president's repeated and angry denunciation of a caravan of poor Central American migrants making their way through Mexico to the USA border.
He repeated that Acosta was a "very rude person", adding, "the way you treat Sarah Huckabee is awful", referring to his White House press secretary. From Acosta's rants to CNN saying this is a threat to democracy, you'd think that the Trump White House tossed a Walter Cronkite-like reporter out onto the street.
Many in the media industry were furious with Ms Sanders for sharing the video, including one of Mr Acosta's colleagues. Trump has repeatedly called him "fake news", turning him into a symbol of the president's general animus toward the news media.
"I worked with Jim @Acosta at CNN".
On Thursday, Sanders tweeted a video purportedly backing up her version of the events.
"Mr. President, I have one other question on the Russian Federation investigation".
Acosta tweeted a video of him surrendering his "hard pass", or press credentials to the Secret Service.
The president then turned to NBC News' Peter Alexander, who tried to defend Acosta. "To be honest. You aren't the best", he hit back.
"I came in here as a nice person wanting to answer questions, and I had people jumping out of their seats screaming questions at me", Trump said.
"We stand by our decision to revoke this individual's hard pass", Sanders captioned a clip from the press conference.