CVE-2026-54171: Excon does not redact additional sensitive/risky headers when following redirects

The redirect follower middleware previously failed to strip a number of headers that are known to be sensitive and did not provide a way to provide a custom list of headers to strip.

What kind of vulnerability is it? Who is impacted? This could cause inadvertent leakage of sensitive data for users of the RedirectFollower middleware in cases where the initial request includes header information that is not intended for the new target.