Firefox behaved slightly differently for already known resources when loading CSS resources involving CSS variables. This could have been used to probe the browser history. This vulnerability affects Thunderbird < 91.9, Firefox ESR < 91.9, and Firefox < 100.
[
{
"vendor": "Mozilla",
"product": "Thunderbird",
"versions": [
{
"version": "unspecified",
"lessThan": "91.9",
"status": "affected",
"versionType": "custom"
}
]
},
{
"vendor": "Mozilla",
"product": "Firefox ESR",
"versions": [
{
"version": "unspecified",
"lessThan": "91.9",
"status": "affected",
"versionType": "custom"
}
]
},
{
"vendor": "Mozilla",
"product": "Firefox",
"versions": [
{
"version": "unspecified",
"lessThan": "100",
"status": "affected",
"versionType": "custom"
}
]
}
]