The Chrome bug — which Google corrected in Chrome version 65 but has resurfaced in Chrome 67 — allows scammers to give users the impression they’re experiencing a serious operating system error and need to hire a professional to correct the issue, Ars Technica reports.

The technique first gained attention in February and exploits a vulnerability that allows it to force the browser to save a file over and over again, so fast that users don’t realize what’s happening. After 5-10 seconds, the browser freezes and then posts a phone number for you to call for “support” to correct the issue.

The issue also impacts Firefox users. Both companies told Ars Technica they are aware of the issue and are working on addressing it. In the meantime (and in general), if you receive a pop-up from a website suggesting your computer is having issues, don’t call that number. In most cases, the error can be addressed by force quitting your browser or restarting your computer.