A new Twitter update that allows people to see when other users are online has been criticised for leaving people vulnerable to cyber stalking.
Renowned security expert Graham Cluley was among dozens of industry figures to question the new feature, which was introduced to a limited number of Twitter users.
"Good news for stalkers. Twitter is thinking of telling you who's online right now," Mr Cluley tweeted, along with a sad face emoji.
Status indicators bring Twitter in line with other popular apps, such as Facebook, and are designed to make the platform more "conversational".
The new update comes alongside something called threaded conversations, which means replies to tweets are easier to follow.
Sara Haider, Twitter's director of product management, announced the updates over Twitter and received almost 3,000 replies.
"Hey Twitter, we've been playing with some rough features to make it feel more conversational here," Ms Haider tweeted. "Still early and iterating on these ideas. Thoughts?"
Dozens of replies included criticism of the online status feature, with many Twitter users saying they disliked apps that showed online status for privacy reasons.
Ms Haider responded to one sceptical Twitter user by saying the platform is experimenting with ways to signal specifically when someone is online and looking to have a conversation.
"There's something about being avail for conversation *right now*," she tweeted. "Like for example, checking Twitter silently while distracted a meeting, vs being on the train for 45 mins [sic]."
In a separate response, Ms Haider said users should be in "full control" of showing their online status.
Privacy advocates have previously criticised Twitter for failing to adequately protect its users from harassment.
Other new updates that Twitter is currently considering include a feature that suggests which accounts someone might want to unfollow.
A recent trial of the function was recently carried out to see if it would boost user engagement, though it is unclear whether Twitter plans to roll it out on a wider scale.
