There seems to be something wrong on some Microsoft servers if you get the SEC_ERROR_OCSP_INVALID_SIGNING_CERT error message. They may have signed the OCSP response with a certificate that Firefox can't chain to a built-in root certificate. Hopefully they fix this quickly on affected servers.

This looks like a problem with OCSP Stapling on the server because it works when I disable OCSP Stapling in Firefox.

• https://en.wikipedia.org/wiki/OCSP_Stapling
• https://blog.mozilla.org/security/2013/07/29/ocsp-stapling-in-firefox/

You can temporarily toggle this pref to false on the about:config page to disabling OCSP Stapling works for you. It is best to reset this pref via the right-click context menu to true once you are done with the affected website.

• security.ssl.enable_ocsp_stapling = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

Ok I will try again later and if it still doesn't work I will try the about:config

This error message appears after the latest Windows 10 upgrade to Windows 10 Home - v1703, OS Build 15063.296 I was able to access web mail successfully today before the upgrade was applied.

I am still having this problem today. It started around noon yesterday. The about:config fix works but I am worried about doing all my internet stuff and going through hundreds of emails and paying my bills while doing this. Will it make it unsecure for this or am I ok?

It did happen around the time of microsoft updates which I download myself but they did not fix it and it happened before I downloaded them. I am on windows 7 not 10 so I don't think the windows 10 update is the issue. Is there a real fix? and are others having this issue with live.com this weekend?

Hi

Microsoft are currently working on resolving this issue which is impacting many people. The fix recommended above is a temporary measure until this is in place, hopefully in a couple of days.

I'll point out that this problem seems NOT to be affecting other browsers -- IE 11, Vivaldi in my case. On the other hand, F'fox 53 on both a Windows 7 64-bit system and LinuxMint 32-bit system remain affected as of Monday morning, 29 May, 2017 at 11:15 AM PDT...

Echo RBV's comments. I was able to get to MS web Mail using Edge.

This morning at 7am PDT the problem seemed resolved as I had no problem signing into MS web mail using Firefox.

RBV said

I'll point out that this problem seems NOT to be affecting other browsers -- IE 11, Vivaldi in my case. On the other hand, F'fox 53 on both a Windows 7 64-bit system and LinuxMint 32-bit system remain affected as of Monday morning, 29 May, 2017 at 11:15 AM PDT...

The problem lies with Microsoft, whose servers   (in layman's terms)   send an expired assurance that their SSL certificate is still valid. Unfortunately it turns out that Firefox is the only browser checking for this on each secure https site it is loading. (whereas other browsers glance over that and only check for  : https://en.wikipedia.org/wiki/Extended_Validation_Certificate).