Facebook announced that thousands of users worldwide may have been targets of hacking attempts by private surveillance companies.

Cyber-mercenaries who engage in “surveillance-for-hire” work used the company’s tools in an attempt to hack roughly 50,000 users, according to a report released on Thursday by Meta, the parent company for the social media network. Meta said it alerted the users about the cyber-mercenaries, which consisted of surveillance companies that a handful of governments had working relationships with.