if it’s system window you can use :
@ferrariklersone Have you tried to make a TestObject of the Annuler button and then WebUI.click(‘button_Annuler’)? The TO could be as simple as text() equal ‘Annuler’.
@grylion54 Yeah guy I tried several methods, but nothing worked.
The popup window is not linked to the browser, but the site which imposed it by a plugin already installed on the machine.
I tell myself that this scenario cannot be automated, it would just be necessary to use manual tests because the complexity makes automation very difficult in this case.