I've encountered similar oddities, seeing the remnants of other users' sessions, but no mouse movements so I guess they'd been recently terminated.

Also the VMs aren't locked down as tightly as they ought to be, last time I poked around in the Windows ones there were a few folders left writeable that shouldn't have been, ones with executables and scripts in used to control it.

That said, their service is so very useful that I continued using them anyway. My use case is just to occasionally check some public-facing websites are rendering properly on various browsers, so no big deal if someone snoops on that.

I really saw mouse movement and url typing, even though it was only a few seconds.

I raised the issue with them back in July 2013, but was initially brushed off. A couple more aggressive emails and they finally responded after 2 weeks saying the issue had been solved.

Haven't had problems since, but still wary..

Sorry I didn't mean to sound like I was doubting your account, was intended as a confirmation of your sightings!

It's just as probable that I connected in while the users were idling.

No worries! Just pointing out the fact that they didn't seem too worried about the issue when first notified, and I really had to press to get some attention.

Pity I wasn't fast on a screen capture!

Same here, in Nov 2011. I contacted support, told them about it, and cancelled my account/sub right away back then -- I was using Browserstack for developing client sites and applications, and didn't feel like getting sued over a service I am using potentially leaking sensitive information.

that happened to customers at a company I worked for. Turned out to be awful handling of threading in a rails app caused sessions to get mixed up.

Is there a good browserstack alternative?

The only other 2 I could think of is SauceLabs and Rainforest QA.

I think browserling is a similar service.

browserling.com

Good. Probably no. But there is Saucelabs.

There is, actually; Crossbrowsertesting.com .. it's good.