What security software do you have? Enabling ImportEnterprisesRoots is usually done by security software to be able to monitor (intercept) your internet traffic by injecting its own certificate in Firefox (i.e. act as a MITM). Without this root certificate Firefox would show an untrusted error on all secure HTTPS connections. Some known security software includes AVG and Kaspersky. *https://support.mozilla.org/en-US/kb/error-codes-secure-websites