"We have a responsibility to protect your data, and if we can't then we don't deserve to serve you," wrote Zuckerberg. "I've been working to understand exactly what happened and how to make sure this doesn't happen again."
Zuckerberg went on to say that Facebook made some mistakes along the way with regards to handling the mismanagement of users' private data, but stopped short of offering up a full apology for the debacle. He provided an expanded history of what took place, and how Cambridge University researcher Aleksandr Kogan was able to access and weaponize the data siphoned from his personality quiz app that installed by around 300,000 Facebook users. However, since the data from those users' friends whose privacy settings allowed unfettered data access -- even if they hadn't installed the app -- was also accessible, Kogan was able to amass the personal details of roughly 50 million Facebook users.
"In 2015, we learned from journalists at The Guardian that Kogan had shared data from his app with Cambridge Analytica," Zuckberg added. "It is against our policies for developers to share data without people's consent, so we immediately banned Kogan's app from our platform, and demanded that Kogan and Cambridge Analytica formally certify that they had deleted all improperly acquired data."
Ultimately, that data was never deleted and was used by Cambridge Analytica on political campaigns, including Donald Trump's successful 2016 U.S. Presidential campaign. Facebook banned Cambridge Analytica from using its services last week when it discovered that it was using the data that was supposedly deleted.
"This was a breach of trust between Kogan, Cambridge Analytica and Facebook," added Zuckerberg. "But it was also a breach of trust between Facebook and the people who share their data with us and expect us to protect it."
Moving forward, Facebook has outlined a 6-point plan that it will use to help ensure that the private data of its users is safeguarded from future abuses. These include Facebook alerting users when it determines that an app may have misused their data, turning off apps that haven't been used for an extended period of time, and rewarding people that find vulnerabilities on the platform.
"I started Facebook, and at the end of the day I'm responsible for what happens on our platform," Zuckerberg concluded. "I'm serious about doing what it takes to protect our community. We will learn from this experience to secure our platform further and make our community safer for everyone going forward."