Any line in a 2.4 config file that ended in "=false" was stripped out and ignored. For flag options and boolean options with a default of false this is not a problem, since being set to false and not being present are equivalent. However, for options that default to true and setParameter options that need to be set to false, this results in the options being ignored when set to false in a config file.
All normal options in the 2.4 branch default to false, so the only options affected are some setParameter options that can be set to false but do not have a default of false. It is present in versions of MongoDB between v2.4.0 and v2.4.8, inclusive.
The conditional that skips the lines that end with "=false" in the config file was modified to not skip any line that starts with "setParameter".
To set these options to false, the --setParameter must be used on the command line rather than in a config file.
Production release v2.4.9 contains the fix for this issue, and production release v2.6.0 will contain the fix as well.