When a Web Extension had the all-urls permission and made a fetch request with a mode set to ‘same-origin’, it was possible for the Web Extension to read local files. This vulnerability affects Firefox < 74.
[
{
"product": "Firefox",
"vendor": "Mozilla",
"versions": [
{
"lessThan": "74",
"status": "affected",
"version": "unspecified",
"versionType": "custom"
}
]
}
]