Microsoft has started notifying some Outlook.com users that a hacker was able to access accounts for months earlier this year. Microsoft says the hackers could have viewed account email addresses, folder names, and subject lines of emails, but not the content of emails or attachments. “Our data indicates that account-related information (but not the content of any e-mails) could have been viewed, but Microsoft has no indication why that information was viewed or how it may have been used,” says Microsoft in an email to affected users. “Please be assured that Microsoft takes data protection very seriously and has engaged its internal security and privacy teams in the investigation and resolution of the issue, as well as additional hardening of systems and processes to prevent such recurrence.” This security incident comes weeks after a former security researcher pled guilty to hacking into Microsoft and Nintendo servers. Microsoft confirmed the breach in a statement to The Verge, but the company isn’t revealing exactly how many accounts were affected.