"When you see 'anonymous source,' stop reading the story, it is fiction!"

New York Times reporter Maggie Haberman on Wednesday called out President Donald Trump for his latest Twitter attack on the press. 

This time, Trump targeted anonymous sources and instructed his followers to automatically deem news stories as fiction if they include them.

Haberman, a veteran of New York City journalism familiar with Trump's past antics, pointed out that Trump's dislike of anonymous sources is newfound. He often served as one when he was trying to make a name for himself in New York City.

Trump was known to call newsrooms to make dubious and self-aggrandizing claims on background. He also posed as publicists with fake names like “John Miller” and "John Barron", as reported in 2016 by The Washington Post.

Trump's tweet was in response to a ​CNN report Friday that his former fixer and lawyer Michael Cohen plans to tell special counsel Robert Muller that he was present when the president was told in advance about a now-infamous meeting in Trump Tower between members of the Trump campaign and Russians who had offered dirt to hurt the Democratic presidential candidacy of Hillary Clinton. 

Cohen's lawyer, Lanny Davis, later ​said he had falsely confirmed CNN's report. Even as other news outlets like The Washington Post retracted their versions of the story, CNN stood by its reporting, which it said it did not rely on Davis' account. 

Whether or not CNN missued anonymous sources, many Twitter users pointed out that Trump was in no position to judge. Just hours before his tweet on the subject, Trump tweeted about a Daily Caller report that cited anonymous sources to claim China hacked Hillary Clinton's email server. 

Trump has in the past referred to "credible sources" to attack his opponents. In 2012, he cited supposedly believable informants to back his claim that then-President Barack Obama was lying about having been born in the United States. 

Also, many news stories that Trump has called "​fake news" on Twitter have later ​proven to be true, including some by Haberman. 

When she reported in April that Trump was planning on changing up the legal team advising him on the Russia probe, the president ​called her a "Hillary flunky" and said the story was false. Haberman's story, however, was proved correct shortly thereafter when Trump's lead attorney, John Dowd, resigned and former federal prosecutor and Fox News commentator Joseph diGenova was added to the team.

When The Washington Post reported in March that Trump had decided to remove H.R. McMaster as national security adviser, White House press secretary Sarah Huckabee Sanders ​denied the claims. But sure enough, days later, McMaster was ​replaced by John Bolton.