For native-to-JS bridging, the app requires a unique token to be passed that ensures non-app code can't call the bridging functions. That token was being used for JS-to-native also, but it isn't needed in this case, and its usage was also leaking this token. This vulnerability affects Firefox for iOS < 25.
{
"cpe": "cpe:2.3:a:mozilla:firefox_mobile:*:*:*:*:*:iphone_os:*:*",
"source": "CPE_RANGE",
"extracted_events": [
{
"introduced": "0"
},
{
"fixed": "25.0"
}
]
}