Previously, Firefox allowed to submit a
<form> through an untrusted
submit event generated in a script, not by the user. This Firefox-specific behaviour has been removed with Firefox 69, aiming at improve web interoperability.
// Don't do this form.dispatchEvent(new Event('submit')); // Do this form.submit();
However, the form submit button in YUI 2 is broken due to the change, because it relies on a user-agent detection to call the
submit method only in Chrome, Safari and Internet Explorer. Mozilla is trying to work around the issue on Jenkins that uses YUI, but the chance is, other sites are also affected. If your site still uses the legacy library, you can patch the code in question just like what the Jenkins team did.
Update: The change has been backed out due to the compatibility concerns.