How does Replay/Reissue Responses actually affect the client?

[Lior]

If a site uses, for example, a <script src=... then I want to catch that script and modify it.

I choose Unlock for editing and modify it, but I've noticed when I click Replay/Reissue the browser's console still shows only the original Response.

Meanwhile, Fiddler does show the new modified request being sent.

So what does it mean?

[Boby]

Hi Lior,

"Reissue" functionalities will replay the modified request. In case you modify the response for an already captured session, this shouldn't affect the request, and when the same request is replayed, you server will probably return the same response.

If you want to automatically trick the client to use another script and not the one returned by the server, you can use an AutoResponder rules configured to match the request and return the needed script without reaching to the server. 

Regards,
Boby
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[Lior]

>"Reissue" functionalities will replay the modified request. In case you
modify the response for an already captured session, this shouldn't
affect the request, and when the same request is replayed, you server
will probably return the same response.

In that case, what is it supposed to affect?

[Boby]

Hello Lior,

Reissue will reply the request, with option to edit it before sending to the server (if you choose Reissue and Edit for example). Then the server will respond, and if you want to modify the response, you can set breakpoint after the response is received by Fiddler, but before it's send to the client, and manually edit it, for example by Tools -> Automatic breakpoints -> After Responses. In this case, you'll have to manually edit the response before releasing it to the client. 

Another approach would be to use AutoResponder, which could return pre-defined responses for requests that matches specific conditions (e.g. the URL is exactly www.example.com/something). In this case, the original server is not reached at all. You can drag and drop sessions to the AutoResponder to create rules based on an original request/response pair, and then modify it to return the modified script.

Regards,
Boby
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[Lior]

>Then the server will respond, and if you want to modify the response, you can set breakpoint after the response is received by Fiddler, but before it's send to the client, and manually edit it, for example by
Tools -> Automatic breakpoints -> After Responses.

Is there an immediate way to click reissue, and have Automatic breakpoints automatically catch it?
Usually it has to be defined inside filters.

[Boby]

Hi Lior,

If you are looking for a way to automate the task, you can use FiddlerScript, e.g.:

static function OnDone(oSession: Session)
    {
        if(oSession.url.StartsWith("www.google.com")){
             // This code is to show how to reissue the request, you can modify the original headers/body as needed before sending it.
             FiddlerApplication.oProxy.SendRequest(oSession.oRequest.headers, oSession.requestBodyBytes, sdSessionFlags);
        }
    }

Regards,
Boby
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