OK, this one's almost surely GNOME's fault. ;)

I honestly can't find the Export Certificate button, though. Can you post a screenshot? Also please figure out what version of gcr you have installed on your system.

:-)

Click the lock icon in the location field, click the View Certificate button, right click the certificate. 

gcr 3.20.0-5.1ubuntu1

Epiphany returns an error for sites that don't have a certificate on file (eg https://oo.net). This seems to be the only way to save a certificate in Epiphany.

(In reply to Technical Support from comment #2)
> :-)
> 
> Click the lock icon in the location field, click the View Certificate
> button, right click the certificate.

OK, I can reproduce.

The following fix has been pushed:
aabe746 ui: Fix certificate export dialog to not hang the application

Created attachment 362950 [details] [review]
ui: Fix certificate export dialog to not hang the application

I don't know why -- I guess something must have changed in GTK+ -- but
currently the certificate export dialog does nothing except hang. It
can't receive any user input or anything.

gtk_dialog_run() seems to fix this, so let's use it.

Note we have to adjust the refcounting here now, since if the Cancel
button is pressed the operation will complete before
_gcr_certificate_exporter_export_async returns. The function is still
partially async, but it now blocks until the dialog is closed.

Note: gcr is unmaintained, so this fix will probably not get released for a long time. But it's fixed in master now.

It's nice when everything works :-)

In the meantime, it's not hard to script a workaround using openssl.