Staff at France’s TV5Monde have been filmed with passwords visible a day after the TV network suffered a huge cyber-attack.
Login details for social media accounts could be seen behind a journalist interviewed on France 2.
It comes after hackers claiming to represent jihadist group Islamic State (IS) took TV5Monde off air.
The Paris-based channel told the BBC the visible data was a one-off mistake and was not linked to the attack.
Its TV station, website and social media accounts were all hit on Wednesday night.
Prime Minister Manuel Valls condemned what he called an “unacceptable attack on freedom of information”.
Journalist David Delos was speaking on camera of the “frustration” felt in the newsroom on Thursday when passwords for accounts on Twitter and Instagram could be seen on a dividing screen in the background.
Most were too blurry to be distinguished with the naked eye, but social media users claimed to have been able to decipher YouTube login details.
Footage broadcast on BFMTV also appeared to show a password written on yellow post-it notes and stuck on computer monitors.
A spokeswoman for TV5Monde said passwords were not normally left around in such a way, and the error made in the interview was an isolated case.
‘Threatening the government’
Prosecutors have opened an investigation into the cyber-attack, which French Interior Minister Bernard Cazeneuve said was likely to have been a “terrorist act”.
A message posted by the hackers on TV5Monde’s Facebook site read: “The CyberCaliphate continues its cyberjihad against the enemies of Islamic State.”
They replaced TV5Monde’s social media profile pictures with a masked Islamist fighter.
Mr Cazeneuve promised the government would do “everything to catch those who tried to attack the heart of the French Republic”.
The head of TV5, Yves Bigot, said on Thursday it was not clear whether the hackers had targeted the channel specifically, or used it as a messenger.
“Obviously what they were doing is threatening the French government, the French military and the French policy in the Middle East.”
France is part of the US-led coalition carrying out air strikes against IS in Iraq and Syria.
The channel has not commented on the latest apparent security breach.
TV5Monde regained control over most of its sites about two hours after the attack began on Wednesday and full services were restored by Thursday evening.