Why cloudflare is agressively blocking jdownloader now (with fix)
So its more of a jdownloader issue and not a cloudflare issue, though ultimately cloudflare is the one blocking. Let me explain.
Recently cloudflare has been checking useragent w/ types of tls fingerprint. If you get a missmatch between useragent, tls fingerprint the useragent should support then you get a cloudflare block **even if your IP has good reputation**.
JD2's default UA is "Mozilla/5.0 (X11; Linux x86_64; rv:125.0) Gecko/20100101 Firefox/125.0"
However, its fingerprint is a TLS handshake is performed by Java's JVM, which produces a signature like Java 1.8.x or Java 21.x not like firefox. This is the specific reason its getting blocked, because of the missmatch.
Cloudflare is correctly blocking it because it essentially is holding a sign that says "I didnt bother to configure a proper tls fingerprint, im the most obvious bot possible, please block me" and its getting blocked.
Jdownloader Java TLS stack -> cloudflare edge -> {java tls on a firefox user agent} -> block / bot score too high -> BLOCKED
However if you use cloudflare's warp
Jdownloader Java TLS stack -> cloudflare warp endpoint -> warp's tls stack -> cloudflare edge -> {warp's tls stack on a firefox useragent} -> block / bot score not effected by tls fingerprint -> allowed
warp still sends origin ip to edge (anonomized) for your bot score, so if your origin ip's reputation is too poor to load cloudflare over a traditional browser then ofc you will still be blocked. warp only fixes jdownloader's poor tls fingerprint stack that raises the score enough to give the potential for allowing it to work.
Edit: some reading comprehension issue on the commenters. I said cloudflare warp is the fix and apparently people cant see this? You connect to cloudflare warp and it works. idk what the issue is that 4 separate people got confused.
Edit2: some people were complaining about not giving a tutorial of how to use cloudflare warp. It is an on off switch with zero ambiguity. Copy and paste "cloudflare warp" into your search bar, install it, and toggle the "on" switch. I am surprised anyone had trouble with this.