Embed projects don't work

Expected behavior

Embedding projects (<iframe allowtransparency="true" width="485" height="402" src="https://scratch.mit.edu/projects/embed/178433850/?autostart=false" frameborder="0" allowfullscreen></iframe>) should work

Actual behavior

It says “oh no, you don’t have flash”:

Steps to reproduce

1. Create a random HTML file with the content

<iframe allowtransparency="true" width="485" height="402" src="https://scratch.mit.edu/projects/embed/178433850/?autostart=false" frameborder="0" allowfullscreen></iframe>

1. Open it with your browser.
2. See the iframe say “oh no, we’re having trouble displaying this scratch project”

Operating System and Browser

Windows 10, on Chrome and Firefox - I think it’s not an OS issue though.

[Sheshank-s]

You have to click on the i button… here let me show you a gif @Kenny2github

Sorry for the messed up colors, I use ubuntu, and for some reason all the colors are tinted purple

[colbygk]

My suspicion is that this is related to Chrome and Firefox tightening their security model. I have reproduced this locally with Chrome 62.0.3202.89 (Official Build) (64-bit) on macOS 10.12.6.

When looking at the Security pane from the dev tools for Chrome, I see:

Normally all secure content must be loaded from a secure document. However Chrome does not print any console messages related to the attempted load of flash content. Adding https://scratch.mit.edu:443 to the allow list under Content Settings→Flash→Allow makes no difference.