User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36

Steps to reproduce:

Go to User Generate certificate in Microsoft CA (certsrv)
https://FQDN/certsrv/

Actual results:

Can not choose key strength

Expected results:

Choose key strength

This is how it looks in Safari https://picua.org/images/2019/09/09/1e33e04d0784dbc1f37329b545bd866c.png

I attempted to reproduce this issue, but the link provided appears to be down (server not found). Can you still use the link?

This is our company CA. It is not available over internet. You should have MS CA to reproduce this.
I've tried on 2 independent CA servers with the same result.

I cannot know whether this is valid of even reproducible.

I will set this bug's component as (Core) Security. Please set it as a more appropriate component if it is incorrect.

Thanks. If you need MSCA server to test it, I can set up it for you.

If you can help me reproduce and confirm it, That would be great. I'm waiting for steps to take to do it. Thank you!

Hello, We have the same problem, it doesn't work since the last version of Firefox, when we try an old version it works.

I will consider this issue confirmed since more than 1 users reproduced.
Also, setting the component to (Core) Security. Please set to a more appropriate one if incorrect. Thank you.

Presumably that page uses a <keygen> tag. Support for this tag was removed in bug 1315460.