CVE-2022-22759: Mozilla: Sandboxed iframes could have executed script if the parent appended elements

Severity: Critical

CVSS Score: 9.6

If a document created a sandboxed iframe without <code>allow-scripts</code>, and subsequently appended an element to the iframe's document that e.g. had a JavaScript event handler - the event handler would have run despite the iframe's sandbox. This vulnerability affects Firefox < 97, Thunderbird < 91.6, and Firefox ESR < 91.6.