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I have tested locally although you are able to input more characters than the specified in the maxlength, after blurring the control, the max length will be applied correctly. This behavior could be replicated in Firefox and Chrome, but not in IE.
Please note that this is a browsers related issue and you could easily test the following input element that will reproduce the same behavior:
Nevertheless, you could try to handle the input's element onkeydown
event and implement some custom logic for handling that browser limitation.
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