Firefox has just adopted a stricter Feature Policy [1].

Previously, it treated itch.io <iframe> attributes

allowfullscreen="true" allow="fullscreen;"

as

allow="fullscreen *;"

but in the new version they are interpreted according to [2]

allow="fullscreen 'src';"

This has broken HTML5 in-game fullscreen functionality for me (e.g. fullscreen button in Settings screen).

Similarly, Chrome used to interpret

allowfullscreen="true" allow="fullscreen;"

according to [3]

allow="fullscreen *;"

but that seems to have changed too, introducing the same issue (not sure in which version).

Could itch.io explicitly use

   allow="fullscreen *; ... "

so that everything works again?

[1] https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/74, HTTP
[2] https://developer.mozilla.org/en-US/docs/Web/HTTP/Feature_Policy/Using_Feature_Policy, the iframe allow attribute
[3] https://developers.google.com/web/updates/2018/06/feature-policy, the iframe allow attribute