I tried logging into my Telerik account using the latest FireFox browser and there are a boatload of error messages in the developer's console. I could not do it. I had to go back to Chrome to login to this website.

Also, the latest version of Fiddler which I downloaded and installed yesterday will correctly capture my Intranet Chrome traffic but none of my Intranet FireFox traffic. Where is the support for the FireFox web browser?

I'm not sure how to describe this with any detail.  I have a JavaScript app.  It works fine without Fiddler running.  When I run Fiddler and enable capturing and decrypting of HTTPS, I get JavaScript errors when running the app.  All the other HTTPS stuff I've tried works fine.  (If I turn off HTTPS decrypting, the JavaScript app works too.  So it's something related to HTTPS decrypting.

I tried another product called Charles, and the JavaScript app works fine and Charles captures and decrypts all HTTPS traffic from this JavaScript app just fine.

But I'd rather use Fiddler.  But I can't figure out what the issue might be with Fiddler HTTPS decrypting.

I have already reset the Fiddler certs several times with no change.  Again, all other HTTPS works and decrypts correctly.

Hello Telerik team,
Thanks for Fiddler, it is a powerful tool for testing. I am using Fiddler V5.0.20202.18 for NET 4 on Windows 7.

I am sniffing and capturing HTTPS traffic generated by selenium + chromedriver on YouTube. For testing purposes, I export each test as a HAR file to examine its content.

My problem is that for all exported HAR files, the query string section is empty ("queryString": [],) . Instead if I generate the HAR file using devtool, I get those values.

Can you give me some guide on how I can get this content using Fiddler.

I would greatly appreciate any help,

Hi, we're trying Fiddler everywhere on OSX Mojave, as a replacement to Charles, and it seemed to work when first installed as I got the password prompt, but upon relaunch it now no longer prompts for a password. Clicking the 'Capture button also does nothing.

Any ideas?

Thanks

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   
---------------------------