Image-sharing website Imgur has confirmed that the emails and passwords of 1.7 million users were compromised in 2014.
The data breach has only recently come to light after being discovered by security researcher Troy Hunt.
Mr Hunt said he was impressed with the company's swift response.
Imgur said in a statement that no other personal data had been taken as it did not collect information such as real names and phone numbers.
"We apologise that this breach occurred and the inconvenience it has caused you," wrote Roy Sehgal, Imgur's chief operating officer, in a blog post.
Mr Sehgal said Imgur was "still investigating" but its former encryption method - a hashing algorithm - may have been "cracked with brute force".
Original Source: http://www.bbc.co.uk/news/technology-42137837