Instagram has denied it has been victim to a data breach after many users received emails prompting them to reset their password.
The firm said it had resolved a problem which allowed "an external party" to get the social media platform to send out legitimate password reset requests to users.
Instagram said there had been no breach of its systems, and told users their accounts were secure.
But some experts have questioned the statement, with cyber security firm Malwarebytes claiming the password reset emails had in fact been sent as a result of a hack.