BuzzFeed released a story earlier this week showing that false election news articles outperformed real news on Facebook during the final months of the election. These false news stories generated more engagement on the social network than election stories from 19 major news outlets combined including The New York TimesThe Washington Post, The Huffington Post, NBC News and others.

The false stories ranged from the ridiculous to the scandalous, including an endorsement of President-elect Donald Trump by Pope Francis. One site alone had four stories that were shared 3 million times on Facebook, including one about Hillary Clinton selling arms to ISIS.

At a press conference in Berlin on Thursday, President Barack Obama made an impassioned plea to get serious about fake news “in an age where there’s so much active misinformation.”

“If we are not serious about facts and what’s true and what’s not, and particularly in an age of social media when so many people are getting their information in sound bites and off their phones, if we can’t discriminate between serious arguments and propaganda, then we have problems,” said the president.

This false news trend has also moved into the corporate sector. PepsiCo* had to manage a mini crisis over the last week after a series of false articles on social media claimed that CEO Indra Nooyi told Trump supporters to “take their business elsewhere.” In fact, she said no such thing.

The PepsiCo executive had spoken at The New York Times Deal Book conference. When asked about the election, the first thing she did was congratulate Trump. She called for the country to come together and spoke honestly and candidly about the apprehension some of her employees felt following the election.

Despite these facts, hyper-partisan websites jumped into action distorting the remarks. Some blatantly changed her words to make it appear she was personally attacking the President-elect (which, if you watch the interview like I did, could not have been further from the truth). Before long, the #BoycottPepsi hashtag began to get traction with 19,000 mentions. A handful of mainstream news outlets initially took their lead from social media and got the story wrong.

PepsiCo quickly issued a clarification acknowledging that the CEO had “misspoke” in one instance, noting that she was referring to the reaction of one group of employees and never intended to imply that all of the company’s workers felt the same way about the election results.

As more and more people took the time to examine the evidence more closely, the story began to change. A number of leading news outlets – including Fortune, CNN, The Washington Post, the New York Post and the Financial Times – all exposed the partisan meme and set the record straight. CNN’s headline stated, “Trump supporters call to boycott Pepsi over comments the CEO never made.”

There are important lessons in this for PR executives. Hyper-partisan blogs on both ends of the political spectrum will not let the facts get in the way of a good story – and are unlikely to correct their erroneous posts after they are made. These posts can spread like wildfire via social media. And the mainstream media – itself constantly hungry for content that drives clicks and social media engagement – is susceptible to inadvertently publishing false news without proper editorial safeguards. Now more than ever, the mainstream media must take whatever steps necessary to uphold the highest journalistic standards and act as the arbiter of truth in this unprecedented new age of misinformation. Their ability to do so will dictate whether the public’s trust in the mainstream media continues to erode or begins to rebound.

As Obama lamented to The New Yorker’s David Remnick, we are in a world where “everything is true and nothing is true… The capacity to disseminate misinformation, wild conspiracy theories, to paint the opposition in wildly negative light without any rebuttal — that has accelerated in ways that much more sharply polarize the electorate and make it very difficult to have a common conversation.”

The ultimate question for PR executives remains; when to intervene and when to let a story run its course and die of its own weight. The rise of false news and politicization of the news business has changed the game. When there is a political tinge to the story, there must be immediate clarification of the CEO’s intent and explanation of the context. There must also be a concerted effort to correct errors in mainstream coverage that give opinion blogs the oxygen to keep the story going.

Richard Edelman is president and CEO.

*Edelman Client