Firefox Private Browser - Form Shows but Doesn't Submit

[Daniel_Johanse1]

I recently read through other posts in the Community and the Teknkl blog post about Forms 2.0 and Firefox's Private Browsing mode so we switched our Forms embed code from using app-something.marketo.com to our Marketo LP domain. However, while using Firefox's Strict setting in its Tracking Protection, the form is displaying as expected but it is not submitting. The button changes to "Please Wait" but does nothing.

Additional details:

1. You can test the behavior with the form at the bottom of this page
2. Our main domain and Marketo LP domain both use SSL
3. The form submits as expected when Firefox's Private Browsing is set to "Standard" but not "Strict"
4. I tested using Firefox 70.0 on a Mac and 20.0 on iOS
5. When inspecting the page, I do still see JS loading in the sources from app-something.marketo.com but our developer told me that that is being loaded from the Marketo LP domain embed. When they removed the Marketo LP domain embed, they said it also got rid of the JS coming from app-something.marketo.com

While using our Marketo LP in the embed fixes the form display issue, is this behavior expected with Strict mode in Firefox's Tracking Protection, or is there anything else wrong with our implementation.

Please let me know if I missed any important details, and thank you for the help!

[SanfordWhiteman · Accepted solution]

See my fix at https://nation.marketo.com/message/216081-mktoforms2-is-not-defined-in-marketo-forms-2-cross-domain-... 

[Daniel_Johanse1]

Thank you so much for the quick response. Sorry, I had searched the forums but didn't come across the post you linked to. We implemented your fix and it worked like a charm. Again, thank you very much for the help!