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Forum inaccessible. Server blocks my user agent and responds with 403 Forbidden.

Posted: Thu Aug 21, 2025 9:19 pm
by NilsH
Hello!
For several weeks, possibly over a month now, I have been unable to access this forum.
I always get a "403 Forbidden" response from the server.

At first I assumed that the forum was down for maintenance and the admins needed some time to get it working again.
But after several weeks I figured that maybe something on my side is causing the problem, and I started troubleshooting.

Now I found out that the 403 response is sent depending on the user agent string that the browser sends in the HTTP request.

The default user agent of my browser is:

Code: Select all

Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:109.0) Gecko/20100101 Firefox/115.0
Note the version number 115.0 at the end. It turned out that the server blocks requests with versions from 110.0 to 123.0.
Versions up to 109.0 or 124.0 and above work fine.

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works:
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:109.0) Gecko/20100101 Firefox/109.0

doesn't work:
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:109.0) Gecko/20100101 Firefox/110.0
through
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:109.0) Gecko/20100101 Firefox/123.0

works:
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:109.0) Gecko/20100101 Firefox/124.0
This is independent of the operating system in the user agent string.
If I put in the string for a Linux system "(X11; Ubuntu; Linux x86_64; rv:141.0)", the result is the same.

I hope this can be fixed, so that I don't have to use some addon to fake the user agent.

Regards,
Nils

P.S. Please, no comments about me still using Windows 7. It's the only operating system that fulfills my requirements for an OS. At least until my own OS is finished, which can only be a matter of decades.

Edit: Looks like I'm not the only one having this issue: viewtopic.php?p=642861.

Re: Forum inaccessible. Server blocks my user agent and responds with 403 Forbidden.

Posted: Thu Aug 21, 2025 11:12 pm
by idle
it also blocks edge on windows.

Re: Forum inaccessible. Server blocks my user agent and responds with 403 Forbidden.

Posted: Fri Aug 22, 2025 11:12 am
by Fred
We were basically under ddos attack by AI bots, so I added such user agent checks. It seems to be back to normal, so it's removed for now, but I will put them back if it occurs again.

Re: Forum inaccessible. Server blocks my user agent and responds with 403 Forbidden.

Posted: Fri Aug 22, 2025 3:17 pm
by NilsH
Fred wrote: Fri Aug 22, 2025 11:12 am It seems to be back to normal, so it's removed for now, but I will put them back if it occurs again.
Thank you very much! Now it works again.

But isn't there a better way to protect against DDoS and bots? An attacker with evil intentions can easily change the user agent of his bots, but for normal users it's annoying, or it might lock them out completely if they don't have enough knowledge about web technologies.

Re: Forum inaccessible. Server blocks my user agent and responds with 403 Forbidden.

Posted: Sun Aug 24, 2025 4:02 pm
by Olli
Strangely, absolutely no problem for me... Puzzled... It should be short...