follow-redirects is an open source, drop-in replacement for Node's "http" and "https" modules that automatically follows redirects. Prior to 1.16.0, when an HTTP request follows a cross-domain redirect (301/302/307/308), follow-redirects only strips authorization, proxy-authorization, and cookie headers (matched by regex at index.js). Any custom authentication header (e.g., X-API-Key, X-Auth-Token, Api-Key, Token) is forwarded verbatim to the redirect target. This vulnerability is fixed in 1.16.0.