Could you create a working reproduction in jsbin or jsfiddle so that we can
take what is going on?  Without concrete code it is hard to track down. 

Here's a trimmed down reproduction of what I'm experiencing - let me know if you need me to clarify anything:

https://jsfiddle.net/jonlejon/o57dcLmt/

I've already written some code to work around this - but it should be noted that this works fine in IE and Firefox, as well as the previous version of Chrome.

Thanks!
Jon

Able to reproduce the issue on windows-7, Mac 10.12.2 and Linux Ubuntu-14.04 using chrome stable version 56.0.2924.87 and canary 58.0.3010.0

This is regression issue broken in M56.Please find the bisect information as below
Narrow Bisect::
===============
Good :56.0.2916.0 --   (build revision 431463)
Bad:: 56.0.2917.0 --   (build revision 431726)

ChangeLog: 
================
https://chromium.googlesource.com/chromium/src/+log/6d47d44ba4c0ba026223adb94d7f236fbc5efa22..ec8e431e9a0f80ace76368ce7edce006f3d409f2

Review-Url: https://codereview.chromium.org/2495583002

rsleevi@ could you please look into this issue if it is related to your change,else please help us in finding the appropriate owner for this issue.

Thanks,

There is no way it can be related to the aforementioned CL. Assigning back for bisect.

After re-bisecting the issue, Please find the bisect information as below
Narrow Bisect::
===============
Good :56.0.2913.0 --   (build revision 430459)
Bad:: 56.0.2914.0 --   (build revision 430837)

ChangeLog:
https://chromium.googlesource.com/chromium/src/+log/5b5a21061a6aa8be7cc3b8b6aafa56256bb91e60..e91b6459cf18e90f2766a68a2487701610213be4

Review-Url: https://codereview.chromium.org/2467263002 

tkent@ could you please look into this issue if it is related to your change,else please help us in finding the appropriate owner for this issue.

Thanks.

My CL looks to related to this issue. I'll take a look.

It seems ko.bindingHandlers.securitytypeahead.update() is called too many times by an additional 'change' event on <input> blur.

> https://jsfiddle.net/jonlejon/o57dcLmt/

This fiddle has a problem with Firefox too with the following step:
 1. Focus on Security field
 2. Type 'm', TAB, TAB

My conclusion is Google Chrome works as intended, and this is due to a site bug.

Since Google Chrome 56, 'change' event behavior is identical with Firefox.

Example:
<input value="" autofocus>
<script>
var i = document.querySelector('input');
i.addEventListener('change', function() { alert('change'); });
i.oninput = function() {
  if (i.value == 'm')
      i.value = 'Macy\'s Inc';
}
</script>

In this example, if you type 'm' TAB, both of Firefox and Chrome 56 dispatch 'change' event. Chrome 55 didn't.

https://jsfiddle.net/jonlejon/o57dcLmt/ has the code specific to Firefox. Even if isFirefox=true with Chrome 56, Chrome still shows the red error message. This difference between Firefox and Chrome 56 is due to a bug of Firefox.  The tickerSelector INPUT element is removed from the document tree when a user selects a company name from the completion box. Then, Chrome correctly dispatches 'blur' and 'change' events though Firefox doesn't.