Uber employees have flocked to an anonymous workplace app called Blind as a sort of catharsis since ex-Uber engineer Susan Fowler Rigetti posted about being propositioned and discriminated against while working for the company, according to Blind’s founder Alex Shin.

Rigetti’s explosive post went viral late Sunday night, leading to more than double an increase of Uber employees signing up to chat with coworkers anonymously, Shin says. And the majority of the discussions center around sexism in the workplace and Uber’s leadership — particularly about CEO Travis Kalanick and Uber’s CTO Thuan Pham, who’s accused of ignoring Rigetti’s claims.

Blind formally launched in July of 2015, onboarding a bunch of big tech companies such as Google, Microsoft and Amazon. Uber employees joined later that same year in October and Shin tells us about 2200 Uber coworkers are actively engaged on the app. It works by only allowing those within the same company to chat anonymously with each other. Those on the app must verify they actually work where they say they do to gain access to a certain work channel through email.

There is also a portion of the app called the Tech Lounge where anyone verified to use the app for their workplace can commiserate with other tech workers from other companies. It was in this section just a few days ago an Uber employee working in HR posted a rumor about 118 San Francisco employees resigning from the company. That post has since been removed from the app but was posted on Twitter by a Fitbit employee who took a screenshot of it and tweeted it out.

https://twitter.com/physicsNcoffee/status/834565366185545728

Uber has denied the claims of a mass resignation and did not want to comment further on Blind. But strangely, a week before Rigetti dropped her post, Uber suddenly blocked employee access to the app on the company WiFi. Again, no comment from Uber on why it would have done that, but Shin tells us it’s the only company to do so.

It could be from fears of possible leaks from one part of the organization to another or to try and stop a post like the one put up on Twitter about mass resignations.

There could also be some privacy concerns as anyone posting anonymously could be open to exposure at some point. Though Shin is quick to point out when asked he doesn’t actually go in to see the actual content of people’s posts and that the app doesn’t track user’s profiles for privacy reasons. He also mentioned Blind implements a patented infrastructure to prevent his team from seeing who the individual posting might be.

But what he can do is a keyword search to see what the hot button topics are. He tells us activity shot right up shortly after the sexual harassment claims went public and that users are now logging on at least 10 times a day, up from an average of 3 to 5 times a day before. Many of the comments mention Susan Fowler and sexual harassment, as would be expected. But, says Shin, quite a few more have been about Uber’s leadership and mention Pham a lot specifically.

We don’t know the exact nature of the sentiment in these comments but one could imagine the worry those working for Uber may have at a time like this.

*Those working inside Uber who would like to anonymously share how they are feeling about Uber’s leadership with TechCrunch can get a hold of this reporter at sarah dot buhr at techcrunch dot com.