vf pages broken in Chrome 80

Question

With Chrome 80 coming in Feb 2020, we did some internal testing of our app and figured out that all embedded vf pages are failing to load (rather it shows home page window inside every vf page). We are not setting any cookie deliberately in our code base. What could be the issue? Sharing code snippet of one of our vf page:

<apex:page standardController="Case" extensions="XYZ_ctrl">
<style>
    body.sfdcBody.apexPageInline{
        margin: 0;
        margin-left: -10px;
    }
</style>
<apex:pageBlock mode="maindetail">
    <apex:pageBlockSection columns="1" collapsible="false">
        <apex:pageBlockSectionItem >
            <apex:outputLabel value="Some Count"/>
            <apex:outputText value="{!SomeCount}"></apex:outputText>
        </apex:pageBlockSectionItem>
    </apex:pageBlockSection>
</apex:pageBlock>

Answer 1

After working through these issues weeks back, we found that Salesforce has changed their documentation concerning this and clarified many things.

For starters, make sure you do the following before testing.

1. They suggest to test with Spring 20.

2. Make sure you have the following settings checked in Session Settings

   Require secure connections (HTTPS)

   Require secure connections (HTTPS) for all third-party domains

We found that the Spring 20 release fixes a lot of issues we had with our custom VF pages in Lightning. Even setup pages (those that had an old layout like custom metadata types) had issues in Winter 20 and Lightning for us. It turned out everything worked well in Spring 20.

The important distinction is that Chrome 80 will release in early February before Spring 20. However, Chrome 80 is not the issue. The issue is concerning a change to how an attribute, sameSite, is handled that is planned to occur for Chrome 80. This specific change won't be made until AFTER Spring 20 is released to customers.

The Chrome 80 release is scheduled for February, but Google doesn't plan to enable the “SameSite by default cookies” and “Cookies without SameSite must be secure” capabilities for Chrome 80 stable users until after the planned completion date of Spring '20 org upgrades on 15 February, 2020.