Tested on localhost using XAMPP.

Unable to reproduce the issue on reported chrome version 63.0.3239.84 and on the latest canary 65.0.3309.0 using windows 10 with the below mentioned steps.
1. Launched Chrome
2. Opened Dev tools by clicking F12
3. Opened console and pasted "document.cookie = "cookiesWarn=1"; //not work" and "document.cookie = "cookiesAAA=1"; // WORK"

After above steps are performed we noticed the cookies are saved . Attaching the screen cast of the same.

@Reporter: Could you please check the screen cast and let us know if we have missed any steps in reproducing the issue. Any further inputs from your end may help us in triaging it in a better way.

Thanks!

Deleted: 798826.mp4 4.0 MB

	798826.mp4 4.0 MB View Download

on possible explanation could be that cookiesWarn already exists as HttpOnly cookie in which case you can't overwrite it from javascript

Yes it could be the problem.

Thank you for providing more feedback. Adding requester "vamshi.kommuri@techmahindra.com" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

OK I tried test in PHP.
1. getting list by $_COOKIE and the name is not in list.
2. prevently I deleted the cookie name in PHP code with past date
3. tried create it in JS and still impossible.

do you have an example URL where I can try to repro?

After I closed Chrome and open it again it works as expected. Hmmm.

ok, thanks

please reopen if you can repro again!