Have recently jumped from v2.3 to v5 and am having issues with a 502 error, "Gateway Connection Failed". This failure seems to be occurring randomly. For example, I can start capturing web traffic just fine, and in this case, I'm using Fiddler to ensure eLearning courses are sending a heartbeat/keep-alive to our Learning Management System.

The keep-alive occurs every minute. I'm experiencing the 502 error following one or more successful keep-alive POST events.

The response header specifically states:

502 Fiddler - Gateway Connection Failed

Cache-Control: no-cache, must-revalidate

[Fiddler] The connection to the upstream proxy/gateway failed. Closing Fiddler, changing your system proxy settings, and restarting Fiddler may help. 
System.Exception Upstream Gateway refused requested CONNECT. 407

 

Can I utilize a FiddlerScript or AutoResponder to keep Fiddler authenticated to the proxy/gateway?

I've noticed recently - on multiple machines - that trying to install Fiddler defaults to an install path as the one depicted below. The same outcome is observed regardless if running setup as a local non-admin user, starting setup as a local non-admin user but running as administrator or simply logging in as an administrator account and starting setup. Yet Fiddler is successfully installed and runs just fine.
One of the other outcomes is that using the Start button to start Fiddler by simply typing its name no longer works - regardless if installing to the default path (present in the picture) or manually changing the install path to Program Files\Fiddler. In the first case that would make sense up to a point at least, since Indexing doesn't look in AppData by default, but not sure why it fails to work in the second case.

The latest attempt to install - and the same result observed as above - was using the latest version available today.

Hey all

I am new to Fiddler, but we are in a position where our current ERP (Dynamics AX 2009) is too old and does not support TLS1.2 (its built on .Net 3.5), therefore pretty much all REST calls do not function. Fiddler came up as an option to be able to override SSL protocols to TLS1.2--which in my proof of concept (installed locally to dev box) is working fine.

However I am a bit confused on how I can actually implement this in a "production-ready" manner as all the calls will come from individual client machines on our network running the AX thick-client (its a standard client/server architecture), so I would need to put this in place somehow to target/override/log only REST calls from this application to specifics hosts (I have this working via FiddlerScript) for any calls coming from our internal network. We would need all other traffic to not be impacted.

I'd prefer not to install Fiddler on every client machine, so does it make sense to stand it up as a proxy server between clients and firewall? Is there a better way?

Thanks

Found an issue when testing HTTPS connection with Composer on macOS.

I used the following steps,

1. Install .NET Core SDK.

2. Run "dotnet new mvc" to create an ASP.NET Core project.

3. Run "dotnet dev-certs https" to configure default development certificate.

4. Run "dotnet run" to launch this project at http://localhost:5000 and https://localhost:5001.

Note that https://localhost:5001 can now be opened in Safari without any problem, as step 3 allows Safari to trust the certificate.

Open Fiddler Composer and try to do the same. The error happens,

==================================

HTTP/1.1 502 Fiddler - Connection Failed
Date: Tue, 19 May 2020 04:19:37 GMT
Content-Type: text/html; charset=UTF-8
Connection: close
Cache-Control: no-cache, must-revalidate
Timestamp: 00:19:37.347

==================================

Raw tab shows an exception,

========================

[Fiddler] The connection to 'localhost' failed.  <br />System.Security.SecurityException Failed to negotiate HTTPS connection with server.fiddler.network.https&gt; HTTPS handshake to localhost (for #13) failed. System.IO.IOException Authentication failed because the remote party has closed the transport stream.

========================

This also triggers an exception recorded on ASP.NET Core side,

========================

dbug: HttpsConnectionAdapter[1]
      Failed to authenticate HTTPS connection.
System.Security.Authentication.AuthenticationException: Authentication failed, see inner exception. ---> Interop+AppleCrypto+SslException: Cipher Suite negotiation failure
   --- End of inner exception stack trace ---
   at System.Net.Security.SslState.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, ExceptionDispatchInfo exception)
   at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.PartialFrameCallback(AsyncProtocolRequest asyncRequest)
--- End of stack trace from previous location where exception was thrown ---
   at System.Net.Security.SslState.ThrowIfExceptional()
   at System.Net.Security.SslState.InternalEndProcessAuthentication(LazyAsyncResult lazyResult)
   at System.Net.Security.SslState.EndProcessAuthentication(IAsyncResult result)
   at System.Net.Security.SslStream.EndAuthenticateAsServer(IAsyncResult asyncResult)
   at System.Net.Security.SslStream.<>c.<AuthenticateAsServerAsync>b__51_1(IAsyncResult iar)
   at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Server.Kestrel.Https.Internal.HttpsConnectionAdapter.InnerOnConnectionAsync(ConnectionAdapterContext context)

=======================

Not quite sure why HTTPS connection failed in this way, but hope it can be investigated and resolved.

We are troubleshooting an issue using Fiddler and wanted to know if Fiddler grabs credentials as part of it's network traffic capture that could be used by others.  Obviously, if it's an unencrypted password being sent then that would work, but with encryption and session management, is it possible for someone to utilize credentials seen in the traffic capture to compromise security?

---------------------------
Awww, Fiddlesticks!
---------------------------
Fiddler has encountered an unexpected problem. If you believe this is a bug in Fiddler, please copy this message by hitting CTRL+C, and submit a bug report at http://www.telerik.com/forums/fiddler.

The composition produced a single composition error. The root cause is provided below. Review the CompositionException.Errors property for more detailed information.



1) Unknown error (0x278)



Resulting in: An exception occurred while trying to create an instance of type 'Telerik.NetworkConnections.NetworkConnectionsManager'.



Resulting in: Cannot activate part 'Telerik.NetworkConnections.NetworkConnectionsManager'.

Element: Telerik.NetworkConnections.NetworkConnectionsManager -->  Telerik.NetworkConnections.NetworkConnectionsManager -->  AssemblyCatalog (Assembly="Telerik.NetworkConnections, Version=0.1.2.0, Culture=neutral, PublicKeyToken=67cb91587178ac5a")



Resulting in: Cannot get export 'Telerik.NetworkConnections.NetworkConnectionsManager (ContractName="Telerik.NetworkConnections.NetworkConnectionsManager")' from part 'Telerik.NetworkConnections.NetworkConnectionsManager'.

Element: Telerik.NetworkConnections.NetworkConnectionsManager (ContractName="Telerik.NetworkConnections.NetworkConnectionsManager") -->  Telerik.NetworkConnections.NetworkConnectionsManager -->  AssemblyCatalog (Assembly="Telerik.NetworkConnections, Version=0.1.2.0, Culture=neutral, PublicKeyToken=67cb91587178ac5a")



Type: System.ComponentModel.Composition.CompositionException
Source: System.ComponentModel.Composition
   at System.ComponentModel.Composition.Hosting.CompositionServices.GetExportedValueFromComposedPart(ImportEngine engine, ComposablePart part, ExportDefinition definition)

   at System.ComponentModel.Composition.Hosting.CatalogExportProvider.GetExportedValue(ComposablePart part, ExportDefinition export, Boolean isSharedPart)

   at System.ComponentModel.Composition.Hosting.CatalogExportProvider.CatalogExport.GetExportedValueCore()

   at System.ComponentModel.Composition.Primitives.Export.get_Value()

   at System.ComponentModel.Composition.ExportServices.GetExportedValueFromLazy[T](Export export)

   at System.ComponentModel.Composition.Hosting.ExportProvider.GetExportedValueCore[T](String contractName, ImportCardinality cardinality)

   at Fiddler.Proxy.() in C:\Jenkins\Fiddler_Windows\workspace\FiddlerCore\FiddlerCore.Shared\Common\Core\Proxy.cs:line 283

   at Fiddler.Proxy..ctor(Boolean isPrimary, ProxySettings upstreamProxySettings) in C:\Jenkins\Fiddler_Windows\workspace\FiddlerCore\FiddlerCore.Shared\Common\Core\Proxy.cs:line 207

   at Fiddler.frmViewer.‹•(String[] ˆ•) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:line 3339

   at Fiddler.frmViewer.‡•(String[] ˆ•) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:line 3163


Fiddler v5.0.20202.18177 (x86 x86) [.NET 4.0.30319.1 on Microsoft Windows NT 5.1.2600 Service Pack 3]
---------------------------
OK   
---------------------------

I've been using Fiddler for a long time (from v1 days) and have had many versions installed. Today, there was an update and during update it stopped saying that it couldn't uninstall the existing version from C:\Program Files (x86)\Fiddler2 and aborted. So, I tried to manually uninstall from Windows 10 Add/Remove as well as by going to the mentioned folder. Fiddler is not present in either (there's no Fiddler2 folder at in Program files folder).

So, I tried the following:

1. Downloaded and installed Fiddler to C:\Program files...

2. Installing to default App Data path

3. Deleting all references to Fiddler from registry and installing

Regardless of what I do, the error when running Fiddler is the same:
---------------------------
Machine-wide installation has been found. Progress Telerik Fiddler is closing now.
---------------------------
Machine-wide Progress Telerik Fiddler installation has been found at C:\Program Files (x86)\Fiddler2\ . Please, use that one or uninstall it before starting the per user Fiddler installation.

 

How do I get around this?

Hi, I'm using Cisco AnyConnect secure mobile client ver. 4.8.00175 on macOS Catalina 10.15.3 to access the Kibana service for Client project. without AnyConnect we cant access Kibana.
I've to capture some network requests from the kibana using Fiddler tools for debugging purposes. but when I start AnyConnect Secure Mobile client Fiddler doesn't work or capture any network traffic and if I stop AnyConnect both Fiddler starts capturing network requests.
Could you please guide me on how to solve this problem it's really urgent.

Thanks.

I'm using Fiddler for Mac on macOS Catalina 10.15.3. I want to capture logs from Kibana running in Google Chrome and to access Kibana i connect vpn using Cisco AnyConnect. but only if i disconnect from VPN fiddler capture network request and if i connect to VPN using Cisco AnyConnect Fiddler doesnt capture any network request from browser.

How do the header values automatically enter the TextView? The header value is random ...  like the example image below

https://i.ibb.co/HtMBPSk/Capture.png