Firefox embedded login returns "request_error"

[markzb]

Hi all,

Our embedded login works with Chrome, IE, Edge, Safari, but with Firefox results in an error of code: “request_error”.

We have two applications. Application 1 is transferring ownership of embedded login to application 2.

Application 1 has no problems with any browser. It is actively working.
Application 2 has problems with only Firefox when someone attempts to login.

In the network console in FF, I see our OPTION calls to our custom domain being stopped by the browser. Specifically, no status, type, size is returned and a broken lock icon is decorated:
“The connection used to fetch this resource was not secure.”

When I inspect the headers for the OPTION XHR calls between Application 1 and Application 2, I don’t see a difference.

This feels like a CORs issues edge case in Firefox, but could use a sanity check or some additional ideas. I suppose it could also be in the Auth0 configuration.

To further complicate this issue, it seems to happen any version of Firefox and I can reply the OPTION call in the developer tools and IT WORKS?!

[markzb]

Turns out Firefox is the only browser which absolutely requires you event.preventDefault when overriding a form submission event. If you don’t, it will looks like your XHR preflights are cancelled due to CORs issues, when in fact you are just navigating away from that event.

[konrad.sopala]

Thanks for sharing that with the rest of community!