I have a widget script (widget.js) deployed on an AWS S3 bucket. This script creates an iframe with its src set to http://localhost:5000.
I embedded widget.js using script tag in my web app. Once the iframe is loaded I am sending message postMessage to http://localhost:5000

Problem:
The postMessage works as expected in normal browsing mode but fails in incognito mode. I suspect this might be due to stricter privacy settings or cookies issues in incognito mode, but I haven’t been able to pinpoint the exact cause.

Environment:

• Browser: Chrome (latest version)
• Operating System: macOS Ventura

Solutions Tried:

• Ensuring correct target origin in postMessage.
• Checking browser console for errors (none found).
• Disabling browser extensions.
• Simplified the code to isolate the problem.

Expectation:

• The post message should work even in incognito mode