Stack Overflow has admitted that “a very small number” of users had their data compromised when the company suffered a cyberattack earlier this month.

The firm behind the world’s largest question and answer site for programmers initially claimed that it had not found evidence of costumer or user data being exposed. It now says the attack, which started on May 5, impacted “approximately 250 public network users” who will be notified about the breach.

Read more: After breach, Stack Overflow says some user data exposed