Microsoft is testing a warning for Windows 10 users not to install Chrome or Firefox. The software giant is in the final stages of testing its Windows 10 October 2018 Update, and testers have spotted a new change that appears when you try to install a rival web browser. “You already have Microsoft Edge – the safer, faster browser for Windows 10” says a prompt that appears when you run the Chrome or Firefox installers on the latest Windows 10 October 2018 Update.

The Verge understands Microsoft is simply testing this prompt for now, and that it won’t appear in the final October update. Microsoft does test feature changes over the course of its updates, but this particular change was not documented in the company’s various blog posts and appeared very late in the testing stages. The prompt may still appear in a future Windows 10 update, but that will depend on feedback to this controversial change.

While the prompts can be turned off, they’re yet another example of Microsoft infesting Windows 10 with annoying ads and pop-ups. Some similar prompts already appear and attempt to push Chrome or Firefox users to use Edge, but this latest one steps up Microsoft’s war against Chrome even further. It’s not clear why Microsoft thinks it’s a good idea to include these irritating prompts, as all they’re likely to do is anger Windows 10 users rather than convince them to switch to Edge.

@MicrosoftEdge What kind of slimy marketing cesspool crap is this Microsoft? I proceed to launch the Firefox installer and Windows 10 pops this up? If I wanted to use your browser, I would. pic.twitter.com/f7jk9sGvYA — Sean Hoffman (@SeanKHoffman) September 11, 2018

Microsoft has previously pushed notifications to Chrome users to tempt them to switch to Edge, used OneDrive ads in File Explorer, and preloaded a variety of crapware apps in Windows 10. Microsoft tried a similar push to force Windows 10 Mail users to use Edge for all email links, but the company reversed the change after a backlash. This prompt is more of an irritating one off when you first install another browser, but the feedback will be another test for Microsoft’s “Windows as a service” model that relies on testers to provide responses to the company’s ongoing changes.

Update, September 12th 4PM ET: Sources familiar with Microsoft’s plans tell The Verge this particular warning won’t appear in the final October update. We have updated the article to reflect this is simply being tested.