I wonder how many other websites are doing such stuff. Lately, KDE Plasma often shows me that audio is being played by Firefox, but no tab in Firefox has the sp

I wonder how many other websites are doing such stuff. Lately, KDE Plasma often shows me that audio is being played by Firefox, but no tab in Firefox has the speaker icon. So far, I have not found which page causes this issue (I don't use AliExpress).