Twitter suffered a data breach affecting approximately 211.5 million user accounts after threat actors exploited a vulnerability in its application programming interface (API). The flaw, introduced in June 2021, allowed attackers to submit email addresses and phone numbers to the API and receive matching Twitter profile data in return. By late 2021, attackers had automated this process at scale, systematically building a dataset that linked private contact information to public profiles. The compiled records surfaced on a hacking forum in early 2023. The exposed data combined email addresses with public profile details including names, usernames, and follower counts. That pairing is particularly sensitive because Twitter was built on pseudonymous identity. Many users kept their real-world contact information separate from their public persona by design. This breach collapsed that separation, making it possible to identify the person behind an account. For activists, journalists, whistleblowers, and others who rely on that separation, the exposure creates concrete risks of harassment, doxxing, phishing, and targeted impersonation. Twitter disclosed an API vulnerability to regulators in August 2022, and Ireland's Data Protection Commission, which oversees Twitter's EU operations, opened an inquiry that resulted in a 5.4 million euro fine in 2023. That earlier disclosure involved a smaller confirmed dataset; the 211.5 million record corpus reflects the full downstream scale of the same underlying flaw. Affected users should treat their email address as potentially linked to their Twitter identity, stay alert to phishing attempts referencing their account, and consider whether their current username or profile information could expose them to unwanted contact.

Real-time social platforms collect user identity, contact details, posts, messages, social graphs, device data, and behavioral engagement signals across public and private communication workflows.

Twitter no longer operates under that name and now exists as X following Elon Musk’s 2023 rebrand of the platform. Even so, the breach remains tied to the Twitter-era service, product design, and API decisions that governed how user identity data could be queried and linked at the time.