Mozilla Firefox 78, Mozilla Thunderbird 78: During RSA key generation, bignum implementations used a variation of the Binary Extended Euclidean Algorithm which entailed significantly input-dependent flow. This allowed an attacker able to perform electromagnetic-based side channel attacks to record traces leading to the recovery of the secret primes.
We would like to thank Sohaib ul Hassan for contributing a fix for this issue as well.
Note: An unmodified Firefox browser does not generate RSA keys in normal operation and is not affected, but products built on top of it might.