I recently upgraded fiddler classic to the latest version, but after the upgrade, my extension file dll did not take effect. Its function is to decrypt traffic, which may be related to the upgrade of fiddler. I read the upgrade description and it seems to be a security-related issue. please help me.

I looked through the documentation and found nothing of value: https://docs.telerik.com/fiddler/extend-fiddler/extendwithdotnet

Fiddler classic the lastest version information:

5.0.20243.10853 [16/05/2024]
fixes:
 Check for updates fails in the beta channel.
 Update third party dependencies to mitigate potential security vulnerabilities.

How to set a dark theme on Fiddler Classic?

After update updating Edge browser to version 124.0.2478.51，when access website I get  "Your connection is not private" 

I have configured Windows to trust Fiddler's root certificate.

I set fiddler " !listen 8889 *.acs.org " and set " fiddler.network.https.SetCNFromSNI true"  It works well  before update edge browser.

After update edge when i access pubs.acs.org it is ok.

but when i access pubs.rsc.org i get   "Your connection is not private" 

 I think this is because someing make fiddler  cannot automatically match certificates .

Please help me fix it ,thanks so much!

 

When accessing the nature website via fiddler, if you check Decrypt HTTPS traffic, error 403 forbidden will appear, unchecked resolve https can be accessed normally. As you can see in the picture below:

hi there

on windows 2022 server when i close fiddler or stop capture traffic

running apps can nor connect tls 1.2

i always get errors for service connecting until start capturing.

What should I do to make the system work properly when the program is closed?

 

Thaks for your help :)

I try many library, last library I try was global-tunnel-ng, but still have no result. Usually I use fiddler to trace various request, my Fiddler listen port 8888, therefore I try to use

I expected to see all request on Fiddler, but there are nothing any request on Fiddler panel. 'localhost' and '127.0.0.1' as ProxyURL also don't working. What I doing wrong?

I try many library, last library I try was global-tunnel-ng, but still have no result. Usually I use fiddler to trace various request, my Fiddler listen port 8888, therefore I try to use

 

  var globalTunnel = require('global-tunnel-ng');
  globalTunnel.initialize({
    host: 'ipv4.fiddler',
    port: 8888,
  });

  // my various request to Google, to AWS and more

  globalTunnel.end()
I expected to see all request on Fiddler, but there are nothing any request on Fiddler panel. 'localhost' and '127.0.0.1' as ProxyURL also 
don't working. What I doing wrong?
 

Hi

I am using Fiddler Classic v.5.0.20242.10753 for .NET 4.6.2 64-bit on Windows Server 2012R2 (don't ask!)

I am also using FiddlerScript in C# mode.  My use case is that I am trying to create a temporary fix for a legacy service that is responding with incorrectly derived values in an XML payload.  I can force all clients of this service to access it via Fiddler as a proxy, and I wanted to use FiddlerScript to modify the response to correct some of the data, as it can be derived from other parts of the response.

I did a very very rough PoC by catching the specific calls in OnBeforeResponse and making an arbitrary change.  What I have then tried to do is use the System.XML XmlDocument object, pass it the response body when instantiating, and working from there.

THE PROBLEM:  I have added "using System.XML;" to the script.  I have also added "C:\Windows\Microsoft.NET\Framework64\v4.0.30319\System.XML.dll" to the References field in Fiddler under Tools -> Options -> Scripting and restarted Fiddler Classic.  However, when saving the script, I get an error "The type or namespace name 'XML' does not exist in the namespace 'System' (are you missing an assembly reference?)"

I have tried just about everything I can think of to make that reference:
 - adding directly to the dll in the Windows dir
 - copying the dll(s) to the same DIR as the Fiddler.exe (as suggested in your docs)
 - adding the XML dlls to the GAC

Nothing I do seems to solve this problem.  I thought it might be a .NET version issue, but I have 4.6.2 installed.

How do I properly reference other .NET assemblies that I want to use in script? 

Thanks,
Steve.

I thought maybe I was imagining this, but I can consistently reproduce it. Problem started with Fiddler Classic, and I then tried Fiddler Everywhere only to see the same behavior:

My dev/debugging environment consists of MS Visual Studio, Postman, and Fiddler running on Windows 10. I always have MS Outlook, MS Teams, and SSMS running as well. I run both Visual Studio, Postman, and Fiddler as Administrator, though I've tried running them in normal mode as part of debugging this problem. It makes no difference.

Any time I start Fiddler, within approximately 15 minutes, Teams is the first app to go down... it suddenly reports "no internet connection" and I can't send or receive messages.

Shortly thereafter, Outlook will start throwing up "invalid security certificate" dialogues. Email send/receive is no longer possible after this point... The Outlook Icon in my taskbar shows a yellow triangle with a black exclamation mark.

Next to go is the ability to make https connections through, for example, Chrome or Edge.  I see errors such as the attached.

Has anyone else experienced this behavior? I've tested extensively making sure just the apps I've mentioned earlier were running. I can run for 24, 48, or more hours without the problem occurring. But if I fire up Fiddler (either Classic or Everywhere), 100% of the time, the networking issues occur. Always.

Any thoughts on what might be going on here? My assumption is that Fiddler is trying to be a proxy for everything on my machine, and it just can't do it for <reasons>. If I remember correctly I can manually tell Fiddler NOT to proxy for certain apps, but this seems tedious. I'm especially worried to suddenly see https disabled for Chrome or Edge, as the Visual Studio applications I'm debugging are APIs that use https...

 

 

I'm having this issue where fiddler will only capture traffic coming from 127.0.0.1:8888, any other traffic is CONNECT, I've tried everything to get it to capture normal.