>Firefox (and Chrome) disable Pin Validation for Pinned Hosts whose validated certificate chain terminates at a user-defined trust anchor (rather than a built-in trust anchor). This means that for users who imported custom root certificates all pinning violations are ignored.
That last sentence is key. From Wikipedia: some browsers "disable pinning for certificate chains with private root certificates to enable various corporate content inspection scanners and web debugging tools. The RFC 7469 standard also recommends disabling pinning violation reports for such certificate chains."
If you add CA certificates for the Wifi they probably (I'm not sure if you can tell it manually to not do that) are added to the system-wide trust store. IE and Chrome check that for CAs, Firefox will soon (https://bugzilla.mozilla.org/show_bug.cgi?id=1265113)
(all this for Windows, I believe the same is true for OS X, Linux depends on your specific your setup)
> If you add CA certificates for the Wifi they probably (I'm not sure if you can tell it manually to not do that) are added to the system-wide trust store.
Internet Properties -> Content -> Certificates -> Advanced
>Firefox (and Chrome) disable Pin Validation for Pinned Hosts whose validated certificate chain terminates at a user-defined trust anchor (rather than a built-in trust anchor). This means that for users who imported custom root certificates all pinning violations are ignored.
That last sentence is key. From Wikipedia: some browsers "disable pinning for certificate chains with private root certificates to enable various corporate content inspection scanners and web debugging tools. The RFC 7469 standard also recommends disabling pinning violation reports for such certificate chains."