@Naveen Kumar M Thanks for posting in our Q&A.
For this issue, it is needed to check some logs to find why this restriction setting doesn't work on Cyberfox browser and Firefox. With Q&A limitation, Q&A is not a good channel for such log analysis issue. So, it is suggested to create an online support ticket to get more help. Here is the support link:
https://learn.microsoft.com/en-us/mem/get-support
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