I suddenly started getting the following error message when using Firefox to access Stack Exchange sites:
An error occurred during a connection to math.stackexchange.com. A required TLS feature is missing. Error code: MOZILLA_PKIX_ERROR_REQUIRED_TLS_FEATURE_MISSING
The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. Please contact the website owners to inform them of this problem.
I should add that I am connecting just fine using Chrome.