Cookies Misusing the Recommended “sameSite“ Attribute

As far as I know it is not CI related issue.
I similar issue in my website (CI v3).
I use some embedded charts such as Google Trends which causes this issue because it does requests to another domain. 

If the source of your problem is similar, then it should be fixed by the external domain (in my case Google Trends should set appropriate headers on the responses) that it uses. 
Besides, I have build a Hybrid mobile app, where embedded Google Trends works fine on Android phone (because they use chrome engine), but because if this warning it does not work on Iphone (because it uses Safari engine).

I checked this issue 2 months earlier, so I don't remember all the details.

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Also, I don't know about the scale of your CI 2 application but it is quite easy to upgrade to CI 3 from CI 2. I have done it couple years ago