After several days of silence, Facebook founder and CEO Mark Zuckerberg has finally issued a statement about the recent reports that political data analytics firm Cambridge Analytica collected data from millions of Facebook users.

In a response posted on Facebook, Zuckerberg admitted that his company has “made mistakes” in the past with user data. Zuckerberg also laid out a plan that will intend to improve the way Facebook handles its users' data.

“We have a responsibility to protect your data, and if we can't then we don't deserve to serve you,” Zuckerberg wrote. I've been working to understand exactly what happened and how to make sure this doesn't happen again.”

Zuckerberg said Facebook will notify all users who may have had their information included in the data set that was purchased by controversial political analytics firm Cambridge Analytica.

The firm is believed to have acquired the data of more than 50 million Facebook users — the majority of whom did not willingly provide the information. The data was acquired through a third-party app that gathered data from the friends of people who installed the application. Facebook no longer allows apps to collect personal data from friends.

In order to better protect user data going forward, Zuckerberg said Facebook will “investigate all apps that had access to large amounts of information before we changed our platform to dramatically reduce data access in 2014.” The social network will “conduct a full audit” of any app with “suspicious activity” and will ban any developer that does not comply with the full audit.

Additionally, Facebook will add new restrictions on how developers can access data from Facebook users. Zuckerberg said the company will remove a developer’s access to data if a user hasn’t made use of an app in three months.

The company will also reduce the amount of data users are required to give an app when they sign in. Zuckerberg said that only the user’s name, profile photo and email address will be provided to developers.

For developers who want more access to user information including posts and other private data, Zuckerberg said they will have to ask Facebook for permission and sign a contract before being allowed to request such data.

Starting next month, Facebook will launch a new tool that will display all of the apps that a person is using and what data those apps have permission to access. The tool, which will be placed at the top of the News Feed, will give users the ability to quickly revoke an app’s permissions to personal data.

It’s worth noting the tool is already available in Facebook’s privacy settings but will be given prominent placement in hopes that users will make use of it.

“I started Facebook, and at the end of the day I'm responsible for what happens on our platform. I'm serious about doing what it takes to protect our community,” Zuckerberg wrote . “While this specific issue involving Cambridge Analytica should no longer happen with new apps today, that doesn't change what happened in the past. We will learn from this experience to secure our platform further and make our community safer for everyone going forward.”