Facebook founder and CEO Mark Zuckerberg will tell lawmakers this week that the social media company plans to significantly increase spending on security even at the cost of its bottom line to prevent the kinds of data leaks and manipulation by fake accounts that have dogged the company in the past two years.

“I’ve directed our teams to invest so much in security — on top of the other investments we’re making — that it will significantly impact our profitability,” Zuckerberg plans to tell Congress, according to his prepared remarks made public by the House Energy and Commerce Committee on Monday. “But I want to be clear about what our priority is: protecting our community is more important than maximizing our profits.”

In 2017, Facebook reported advertising revenues of about $40 billion.

Zuckerberg is set to appear before the panel on Wednesday, after appearing Tuesday at a joint session of the Senate Judiciary and Commerce, Science and Transportation committees. He said in his prepared remarks that the company plans to hire more than 20,000 people by the end of the year to handle security.

Even with a greater focus and expenditure, “security — including and around elections — isn’t a problem you fully ever solve,” Zuckerberg will say. Groups like the Kremlin-backed Internet Research Agency, which had several fake Facebook accounts and spent money on advertising on the platform, “are constantly evolving, but we’ll keep improving our techniques to stay ahead.”

On Monday, Facebook plans to notify the American Facebook users whose data was obtained by Cambridge Analytica, The New York Times reported.

Zuckerberg was slated to have individual meetings Monday with senators in advance of Tuesday’s hearing, including with Florida Democrat Bill Nelson and Republicans Charles E. Grassley of Iowa and John Thune of South Dakota. Grassley is the chairman of the Judiciary panel, while Thune and Nelson are chairman and ranking member of Commerce, respectively.

Watch: Politics and Nominations Abound as the Senate Returns to Washington

Taking responsibility

Zuckerberg’s first congressional appearance comes after nearly two years of revelations and media reports about how the social media company not only was misused by shady groups but also itself allowed third-party app developers to take users’ data. He and Facebook have embraced a legislative proposal, known as the Honest Ads Act, that would impose transparency requirements for online political ads.

In his testimony, Zuckerberg plans to tell Congress that while the company he founded has been used to mobilize support during natural disasters like hurricanes and to organize protest marches, the site did not “do enough to prevent these tools from being used for harm as well.” As the company’s single largest shareholder, Zuckerberg will take personal responsibility. “It was my mistake and I’m sorry. I started Facebook, I run it, and I’m responsible for what happens here.”

Ahead of the congressional hearings, Facebook has been busy cleaning up and has taken several steps to tighten privacy safeguards for users that critics have long called for, including restricting third-party apps from gaining access to data, removing features that allowed hackers with emails to gain access to users’ information and launching an investigation on every app that wants to access the social media site. The company also said it’s testing a tool in Canada that would allow users to see who’s behind all the ads running on Facebook.

The hearing before the Energy and Commerce Committee is likely to examine the full history of Facebook’s handling of its users’ data, stretching back to earlier years and previous presidential campaigns.

The House panel signaled in a background memo that it may also look into how Facebook data was used by President Barack Obama’s 2012 re-election campaign.

The committee cited contemporaneous news accounts of how the Obama campaign worked with Facebook to allow users to sign into the campaign website using the social media site. That in turn “gave the campaign access to both those that signed into the campaign, as well as the ‘Friends’ of such persons — ‘the more than 1 million Obama backers who signed up for the app gave the campaign permission to look at their Facebook friend lists,’” the committee said in its memo. “This gave the Obama for America campaign access to ‘hidden voters’ for which they otherwise lacked contact information.”

The committee also highlighted the 2012 consent agreement between Facebook and the Federal Trade Commission, in which the company agreed not to misrepresent the privacy protections it offers users and the extent to which it provides users’ data to third parties. The FTC is now probing whether Facebook violated that agreement in the case of Cambridge Analytica, a U.K.-based company that is said to have obtained data of more than 70 million Americans after a researcher affiliated with the company ran a quiz and collected data not only on the roughly 270,000 Americans who took it, but also on all their friends.

Upcoming elections

In a nod to Facebook’s global reach, Zuckerberg plans to tell Congress that the company is mindful of its role in upcoming elections in Mexico, Brazil, India, Pakistan and other countries.

On Monday Facebook announced it would work with a group of researchers funded by several foundations to study social media’s role in elections.

The goal is to “understand Facebook’s impact on upcoming elections — like Brazil, India, Mexico and the U.S. midterms — and to inform our future product and policy decisions,” the company said in a statement. “The initial term of the commission will be one year and membership will be determined in the coming weeks. We are keen to have a broad range of experts — with different political outlooks, expertise and life experiences, gender, ethnicity and from a broad range of countries.”

The research effort will be funded by a group of foundations on both sides of the political fence — the Laura and John Arnold Foundation, the Democracy Fund, the William and Flora Hewlett Foundation, the John S. and James L. Knight Foundation, the Charles Koch Foundation, the Omidyar Network and the Alfred P. Sloan Foundation, Facebook said.

Watch: What to Expect, and Not Expect, From the House After Recess