Facebook Embed block and Custom HTML block not working

[westnz]

Context and steps to reproduce

Unmute:
https://github.com/user-attachments/assets/d9b90f21-4704-4a7e-bbc0-bf61edb205b2

Site owner impact

More than 60% of the total website/platform users

Severity

Major

What other impact(s) does this issue have?

Platform revenue

If a workaround is available, please outline it here.

No response

Platform

No response

[kspilarski]

📌 REPRODUCTION RESULTS

• Tested on Simple – Replicated
• Tested on Atomic – Replicated

📌 FINDINGS/SCREENSHOTS/VIDEO

Video content from the report:

When using a Facebook Embed block, the editor displays the message: "Embedded content from www.facebook.com can't be previewed in the editor," and no preview appears. However, clicking "Preview in a new tab" displays the Facebook embed.
When using a Custom HTML block with Facebook embed code, the preview appears correctly in the editor, but does not display when the page is previewed.

Findings from the test:

• Simple site - Only the Custom HTML block preview is visible in the editor; the Facebook Embed block does not display a preview:

• Simple site - on the page preview, only the Facebook embed is visible; the Custom HTML block does not display.

• On both Simple and Atomic sites, Facebook embeds don’t display in the editor but appear correctly in the preview.

• On Simple sites, while iframes aren’t supported, it's still possible to add Facebook iframe embed code in the editor, where it shows up, but it won’t display in the preview or live page. This can be confusing since it was possible to add the iframe code in the editor.

• On Atomic sites, the Custom HTML block works as expected, the embed displays in both the editor and preview.

📌 ACTIONS

• Triaged

[arthur791004]

Closing it via Automattic/jetpack#43132. The custom HTML embed code from Facebook.com will now be converted into an oEmbeddable URL, allowing the preview to display properly on the frontend.