version 5.8.1

• Fixed downloads failing on CDN cookie-challenge links (e.g. ArvanCloud/Cloudflare "307 to self" walls): the downloader now follows same-URL redirects — bounded by MaximumAutomaticRedirections — instead of refusing a redirect whose Location equals the current address, and clears the stale 3xx response headers before re-probing so the redirect target is actually fetched (previously the cached-headers guard short-circuited and the redirect was skipped).
• RequestConfiguration.CookieContainer now defaults to a new CookieContainer, so session/challenge cookies issued mid-redirect are stored and replayed on the follow-up request. Set it to null to disable cookie handling entirely. (Note: this is a minor behavior change — cookies are now enabled by default within a download session.)
• Limitations: this does not defeat JavaScript-based bot challenges (the cookie value must be computed by a browser) nor revive expired signed links — such URLs return a small HTML page with HTTP 200, so inspect the response before assuming a download bug.