The Mechanize library is used for automating interaction with websites. Prior to 2.14.1, Mechanize sends caller-supplied credential headers to a different host after an HTTP redirect. Mechanize#request_headers= is reapplied by Mechanize::HTTP::Agent#request_add_headers even after Mechanize::HTTP::Agent#response_redirect strips per-request headers, and the protected header lists omit Proxy-Authorization and Cookie2. An attacker who controls a redirect target can capture bearer tokens or session cookies supplied through request_headers= or the per-request headers argument, while Mechanize#cookie_jar and Mechanize::HTTP::AuthStore are not affected. This issue is fixed in version 2.14.1.

Affected: RubyGems: mechanize

## Summary

`mechanize` leaked credentials to the redirect target when an HTTP redirect crossed to another host. Credentials set through `Mechanize#request_headers=` leaked even when they were `Authorization`.

## Details

Two defects, both in `lib/mechanize/http/agent.rb`.

**1. `Mechanize#request_headers=` bypassed the redirect strip entirely.** `#request_add_headers` copied `@request_headers` onto every request unconditionally, with no host check, including the request issued after a redirect. The strip in `#response_redirect` mutated only the per-request headers hash and never touched agent state. Because `request_headers=` is the documented way to set a default credential for every request, the header the code explicitly protected — `Authorization` — was the one most likely to leak.

**2. The strip list omitted `Proxy-Authorization` and `Cookie2`.** Only `CREDENTIAL_HEADERS = ['Authorization']` and `COOKIE_HEADERS = ['Cookie']` were removed from the per-request headers hash on a cross-host redirect.

Cookies held in `Mechanize#cookie_jar` and credentials held in `Mechanize::HTTP::AuthStore` are **not** affected. Both are looked up per-URI, so they never follow a redirect to a foreign host. The exposure was limited to headers the caller set by hand.

## PoC

```ruby agent = Mechanize.new agent.request_headers = { 'Authorization' => 'Bearer secret' } agent.get('https://example.test/redirects-to-attacker') # the request to the attacker's host carries "Authorization: Bearer…