A bug in the Miller-Rabin primality test resulted in only a single random
base being used instead of a sequence of such bases. This increased the
probability that a non-prime would be accepted by is_prime or that a
randomly generated prime might actually be composite. The probability
of a random 1024 bit number being incorrectly classed as prime with a
single base is around 2^-40.
Introduced in 1.8.3, fixed in 1.10.8 and 1.11.9
Original bug report: