(CNN Money) -- Mark Zuckerberg is finally breaking his silence five days after a data scandal engulfed Facebook.
The Facebook CEO pledged Wednesday to take a series of steps to protect data and fix what he called a "breach of trust" between the social network and its users.
"We have a responsibility to protect your data, and if we can't then we don't deserve to serve you," Zuckerberg wrote in a Facebook post. "I've been working to understand exactly what happened and how to make sure this doesn't happen again."
Zuckerberg is also set to speak with CNN's Laurie Segall in an interview to be broadcast on "Anderson Cooper 360" at 9 p.m. ET.
News broke this weekend that Cambridge Analytica, a data firm with ties to President Donald Trump's campaign, reportedly accessed information from about 50 million Facebook users without their knowledge.
Facebook says the data was initially collected by a professor for academic purposes in line with its rules. The information was later transferred to third parties, including Cambridge Analytica, in violation of Facebook's policies.
The controversy wiped away nearly $50 billion from Facebook's stock price earlier this week and prompted politicians on both sides of the Atlantic to call for Zuckerberg to testify.
Facebook is now facing lawsuits from investors and users as well as a "delete Facebook" movement. The latest member of the latter: Brian Acton, the cofounder of WhatsApp, which Facebook acquired for $19 billion in 2014.
In his post Wednesday, Zuckerberg said Facebook would further restrict developers' access to user data and promote an existing tool that helps users revoke permissions of apps accessing their data.
Zuckerberg also said Facebook is "working with regulators" conducting investigations into the Cambridge Analytica issue.
"I started Facebook, and at the end of the day I'm responsible for what happens on our platform," Zuckerberg said. "We will learn from this experience to secure our platform further and make our community safer for everyone going forward."
Sheryl Sandberg, Facebook's COO, also spoke out for the first time since the scandal erupted, calling it "a major violation of peoples' trust."
-- CNN's Charles Riley and Jackie Wattles contributed to this report.
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