Fiddler always auto-enable proxy in Internet Options every x mins after being crashed once even though the Fiddler isn't running

[Alex]

My Fiddler crashed the last Friday, and after that, something in the background always auto-enable proxy settings in Internet Options even though the Fiddler isn't running, as a result, I couldn't open any web pages and have to manually disable the proxy, but the proxy would be re-enabled again in few minutes and I have to repeat that again and again, any advice to identify and fix that? Thank you.

[Eric R | Senior Technical Support Engineer]

Hi Alex,

Generally, Fiddler doesn't automatically attempt to reestablish itself as the Proxy as this could lead to an infinite loop. Something like this might be caused by VPN Software, Firewall Clients or even Group Policy/Login scripts. In order to troubleshoot this I'll need more information. Can you provide the following information?

1. Screenshot of the Proxy Settings when Fiddler is running? 

2. Screenshot of the Proxy Settings when Fiddler is not running?

3. Screenshot of the Fiddler Connections Tab in settings? To find this go to Tools -> Options -> Connections

4. Output of the Fiddler Log Tab? To get this, select all items in the Log Tab and right-click -> Save to file.

Once I have this information I will be able to provide a more thorough response. Thank you and I look forward to your reply.

Regards,

Eric R | Technical Support Engineer
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[Alex]

Hi, Eric

 

Sorry for being late, I have attached the info you asked, looks like this might be caused by other software? But I didn't install any new software or make settings changes that day, and this issue occurred only after my Fiddler got crashed once.

 

-= Fiddler Event Log =-
See http://fiddler2.com/r/?FiddlerLog for details.

01:13:17:1730 Fiddler Running...
01:13:17:5580 Windows 8+ AppContainer isolation feature detected.
01:13:20:0089 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:29:5808 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:31:3268 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:31:4858 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:32:2158 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:33:8188 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:35:3328 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:35:3348 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:35:3368 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:36:7307 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:38:2097 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:39:9177 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:46:4836 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:49:0026 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:13:49:6176 Assembly 'D:\Users\Alex Chen\AppData\Local\Programs\Fiddler\CertMaker.dll' was not found. Using default Certificate Generator.
01:13:49:7486 /Fiddler.CertMaker> Using .‰+˜ for certificate generation; UseWildcards=True.
01:14:05:9714 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:14:36:0850 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
01:15:01:8377 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance

 

 

Regards

[Eric R | Senior Technical Support Engineer]

Hi Alex,

Thank you for providing the requested information. This does help. Although, it doesn't appear to be an issue with Fiddler but I can try to provide some insight into what I think may be the cause. The items that are suspicious to me are in the Connections tab and the Proxy Settings after Fiddler has been shutdown. Let me explain in more detail below.

Default Connections Tab

Below is a screenshot of my Connections tab when I open Fiddler. Note the Textbox containing the DefaultLAN entry. In yours there are 2 additional entries for VPN's. I recommend reviewing where those VPN connections are being created and removing them unless they are required.

The 'windows10.microdone.cn' Bypass Entry

Below is a screenshot of the Proxy settings after I shutdown Fiddler. There is something that is adding the windows10.microdone.cn to your Proxy settings upon shutting down Fiddler. It might be a virus or malware, I am not sure. But I assume it to has something to do with the VPN entries mentioned above. 

I hope this helps! Please let me know if you need any additional information. Thank you for using the Fiddler Forums!

Regards,

Eric R | Technical Support Engineer
Progress Telerik

[Alex]

Thanks Eric, really appreciated for your quality and quick response!

I agree, that should be caused by some other software/service I'm not aware of for now, I tried to remove the VPNs and also the plugin which added the windows10.microdone.cn but still no luck, I decided to rebuild my PC to fix it.

So let's close this thread, thanks again for your support!