Sen. Elizabeth Warren's (D-Mass.) 2020 campaign has sponsored ads on Facebook falsely claiming the tech company's CEO, Mark Zuckerberg, endorsed President Trump for re-election, Bloomberg reports. Why it matters: Warren quickly let people know that the statement was a lie, but used the opportunity to showcase a hole in Facebook's policy "to exempt politicians' ads from its third-party fact-checking program, " writes Bloomberg. Under Facebook's current fact-checking policy, Trump's campaign has been able to share ads that claim former Vice President Joe Biden promised Ukraine a $1 billion if they fired a prosecutor — a claim that Biden vehemently denies, per Bloomberg. Background: Warren has consistently gone after Facebook and Zuckerberg on the campaign trail, with calls to break up the social media giant. Zuckerberg has previously said he will fight Warren's attempt to break up the company if she wins the election. What she said in the ad: In response: “If Senator Warren wants to say things she knows to be untrue, we believe Facebook should not be in the position of censoring that speech, ” said Andy Stone, a spokesman for Facebook, in a statement to CNN. Go deeper: . .