I've been using Firefox Containers for over half a year now (I use it with the Temporary Containers[1] extension). For most parts, it's working great.

However, whenever I encounter pop-up sign-in pages, such as for older websites and some Firefox extensions, the resulting user session cannot be accessed by the original page or extension. This is even if I open the pop-up with the same container, or with the 'No container' option.

[1] https://addons.mozilla.org/en-US/firefox/addon/temporary-con...