It seems like Yahoo may have been the victim of yet another cyber attack.
On Wednesday, the company issued a warning to users of “potential malicious activity” on their email accounts between 2015 and 2016.
Yahoo said it has started informing users that their accounts may have been “potentially compromised”.
However, the company did not elaborate further or offer any information regarding how many users may be affected.
The following warning message has been sent to users:
“Based on the ongoing investigation, we believe a forged cookie may have been used in 2015 or 2016 to access your account.”
After receiving the message, some users began sharing it on Twitter.
“As we have previously disclosed, our outside forensic experts have been investigating the creation of forged cookies that could have enabled an intruder to access our users’ accounts without a password,” the company said in a statement.
“The investigation has identified user accounts for which we believe forged cookies were taken or used.”
Yahoo later released a statement saying it had: “invalidated the forged cookies so they cannot be used”.
The news comes after Yahoo admitted last September that it had been the victim of a cyber attack back in 2014 where hackers stole the personal data of more than 500 million users.
In December in then admitted another cyber attack had taken place in 2013, which affected more than one billion users, in what was another embarrassing episode for the former internet leader.
Also on Wednesday, Reuters reported Verizon had agreed a cut price deal to buy Yahoo.