Facebook cofounder and CEO Mark Zuckerberg’s net worth fell $5.1 billion, as a data firm was accused of improperly gleaning information on more than 50 million users, according to Forbes magazine.

Zuckerberg, who owns about 16% of Facebook’s shares, is now worth an estimated $69.5 billion.

As a result, he is now sixth on Forbes’ list of the world’s wealthiest people.

During Monday’s transactions, Facebook shares dropped by more than 7%, and the company’s market value dropped to $37 billion.