UserAgent: Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

Example URL:
https://jsfiddle.net/sobahqud/

Steps to reproduce the problem:
1. Open the page with outer fieldset disabled

What is the expected behavior?
Inner fieldset legend's checkbox is disabled.

What went wrong?
Inner fieldset legend's checkbox is enabled.

Does it occur on multiple sites: Yes

Is it a problem with a plugin? No 

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 56.0.2924.87  Channel: stable
OS Version: 6.3
Flash Version: Shockwave Flash 24.0 r0

From most of the descriptions I could grab it states that disabled attribute for fieldset "causes all the form control descendants of the fieldset element, excluding those that are descendants of the fieldset element's first legend element child, if any, to be disabled". It doesn't look like legend of inner fieldset has anything to do with first legend element child of outer fieldset so as far as I understand it should be disabled. Also this behavior makes most sense for me. Firefox also behaves that way.