Environment:
Operating system: Windows 10
Firefox version: Nightly 104.0a1 (2022-07-06)

Preconditions:
Private browsing On
Clean profile

Steps to reproduce:

1. Go to: https://www.msn.com/ja-jp/feed
2. Observe the page

Expected Behavior:
The page loads correctly.

Actual Behavior:
The page is actually blank.

Notes:

1. Screenshot provided
2. Not reproducible on Chrome Incognito mode
3. Not reproducible on FF Release in Private Window
4. Not reproducible on FF release and Nightly while browsing in normal mode

FYI,
Toggling dom.indexedDB.hide_in_pbmode.enabled in about:config seems to fix this issue in pbmode.

Oh no, this looks worse, class hi{constructor(){this.idb=indexedDB} causes breakage. I wonder this is also from some library?

Mozregression

Last good revision: 80116c1aa5c8532275bdd113ce2c431df4f0d994
First bad revision: e64c83e9d62d19e3f8da181736595423b2bddb52
Pushlog: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=80116c1aa5c8532275bdd113ce2c431df4f0d994&tochange=e64c83e9d62d19e3f8da181736595423b2bddb52

Set release status flags based on info from the regressing bug 1776109

It seems that msn.com assumes indexedDB is always defined. I can try to write a shim to meet its expectation, as it's the only site so far that is broken by making that assumption (but we may very well soon find more).

https://www.msn.com/ja-jp/feed accesses indexedDB as a global variable and thus it throws undefined identifier error when it's not defined. Returning null fixes the regression.

MSN does have a feature detection but it's like this. It surely won't work 🤔

export class IndexedDb {
    constructor() {
        /** IndexedDb object */
        this.idb = indexedDB;
    }
    /**
     * Returns if IndexedDb is supported.
     * @returns true if supported else false.
     */
    get supported() {
        if (!this.idb) {
            return false;
        }
        return true;
    }

https://hg.mozilla.org/mozilla-central/rev/4081bdd1be9d

Reproduced this issue on an affected Nightly build 104.0a1 (20220706214039).
Verified as fixed on Firefox 104.0b8 (20220809195844), on Windows 10.