This affects the package clearance before 2.5.0. The vulnerability can be possible when users are able to set the value of session[:returnto]. If the value used for returnto contains multiple leading slashes (/////example.com) the user ends up being redirected to the external domain that comes after the slashes (http://example.com).
{
"source": "CPE_RANGE",
"cpe": "cpe:2.3:a:thoughtbot:clearance:*:*:*:*:*:*:*:*",
"extracted_events": [
{
"introduced": "0"
},
{
"fixed": "2.5.0"
}
]
}