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Thread: [6.6.0 classic] ignores Ext.USE_NATIVE_JSON setting.

    You found a bug! We've classified it as EXTJS-27512 . We encourage you to continue the discussion and to find an acceptable workaround while we work on a permanent fix.
  1. #1
    Sencha User
    Join Date
    Jan 2016

    Default [6.6.0 classic] ignores Ext.USE_NATIVE_JSON setting.

    When we force Ext.USE_NATIVE_JSON = false and use a store with JSON reader (, the class ignores the fact we want to use ExtJS own implementation of JSON decoding and creates a XMLHttpRequest object with responseType = 'json' on browsers supporting XHR2 protocol (Ext.supports.XHR2 == true).

    This effectively makes the response not to be decoded by Ext JS, bypassing its implementation and breaking previous applications that worked with Ext JS 6.5.3-.

    While this is not a very trivial problem to understand, the fix is pretty trivial. Just add a && Ext.USE_NATIVE_JSON condition to, on line 326.

    I've written a fiddle that tampers the next method called right after it calls doRequest() to show how it is setting the XMLHttpRequest object in different scenarios, and also implements a fix (that's triggered by clicking a button) to the issue:

    I hope the fiddle above helps illustrating the issue. Notice the browser should be XHR2-capable (Ext.supports.XHR2 must return 'true') for the issue to be reproducible. The main problem of this, is it imposes a breaking change to applications that used to explore the uncommon (or wrong) JSON syntax as return data, or simply opted out of using browsers' native JSON, even knowing about the XSS risks involved in Ext JS own implementation of Ext.decode().

  2. #2
    Ext Support Team
    Join Date
    Jan 2018


    Hello, hope you are doing well.

    Thank you for reporting this to us, I have identified this to be a bug, I will go ahead and update this in our bug tracker. The reference number will be attached here for you to be able to track the progress.

    Sencha Support.

  3. #3
    Sencha Staff
    Join Date
    Sep 2017


    Thanks for the report! I have opened a bug in our bug tracker.

  4. #4
    Sencha Premium User
    Join Date
    Feb 2012
    Berne, Switzerland


    Same problem here. Ajax requests with [6.6.0. classic] break most of my apps when I migrate them from [6.5.3]!

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