A <dialog> element could have been manipulated to paint content outside of a sandboxed iframe. This could allow untrusted content to display under the guise of trusted content. This vulnerability affects Firefox < 121.
{
    "availability": "No subscription required",
    "binaries": [
        {
            "binary_name": "firefox",
            "binary_version": "121.0+build1-0ubuntu0.20.04.1"
        },
        {
            "binary_name": "firefox-dev",
            "binary_version": "121.0+build1-0ubuntu0.20.04.1"
        },
        {
            "binary_name": "firefox-geckodriver",
            "binary_version": "121.0+build1-0ubuntu0.20.04.1"
        },
        {
            "binary_name": "firefox-mozsymbols",
            "binary_version": "121.0+build1-0ubuntu0.20.04.1"
        }
    ]
}