It would be great to have firefox (or the next firefox-esr) in buster-backports, as it has important new functionality relevant for privacy and data protection, such as the multi account containers function. However, this bug prevents firefox from entering testing, which in my understanding implies, that it cannot make it into backports as well. Is there some way of getting an up-to-date firefox version into stable? For now I work with the binary directly downloaded from mozilla.org, but this is a kludge.