[fixed upstream] Uploaded images disappear when moved if no alt tag is set in Chrome/Edge on Windows

Problem/Motivation

This is an upstream CKEditor issue since 40.2.0, but affects the current build in Drupal 10.2 and is difficult to catch in testing.

Steps to reproduce

• Open a CKEditor instance (including the demo builds at ckeditor.com) in a Chromium browser
• Upload an image, either by clicking the "Upload image from computer" button, or dragging one onto the editor
• Wait for the image to fully upload
• Drag the image to a new location without setting the alt tag, or setting it to decorative
• The image will disappear

The issue is reproducible during the session that they are first uploaded and during subsequent sessions.

The behaviour is consistent when adding or removing the alt tag using the source browser. Without an alt tag, or with an empty alt tag (alt=""), the image disappears as soon as it moves, with an alt tag (even containing just a space), the image moves around as you'd expect.

All Chromium browsers on Windows appear to be affected, but not MacOS or Linux.

Proposed resolution

The only current solution is to disable the Link plugin, which obviously isn't practical. This will presumably need a fix upstream, but potentially will impact Drupal users running 10.2.x.