Wikimedia Bugzilla is closed!

wfRandom returns a value greater than 1 with a probability of ~2^-31 (if
mt_getrandmax == 2^31-1). I don't think that will cause any problems, but a
comment in the code says the value should be between 0 and 1.

Here is a "correct" version of the function:

function wfRandom() {
    # The maximum random value is "only" 2^31-1, so get two random
    # values to reduce the chance of dupes
    $max = mt_getrandmax() + 1;
    $rand = number_format( (mt_rand() * $max + mt_rand())
        / $max / $max, 12, '.', '' );
    return $rand;
}