In a first for the European regulator, Twitter has been fined 450,000 euros for a breach of the EU’s GDPR data privacy regulations.

This was a ground-breaking penalty, the first time the Data Protection Commission has fined a major US tech company.

Twitter admitted the error and said it was due to low staffing levels between Christmas Day 2018 and January 1, 2019. The rules specify that a data breach must be notified within 72 hours.

News of the fine came on the same day that the European Union announced its new regulations for big tech.