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Unable to load website if any background XHR request is failed

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I am using Firefox Developer Edition Version: 110.0b5 (64-bit) on M1 Mac running Ventura 13.1.

I am building an webapp some XHR triggering in background but it is not necessary to run the application (running fine on other browsers). But on Firefox Developer Edition, It shows a error window with the message and stops loading the application.

Firefox can’t establish a connection to the server at localhost:4000.

localhost:4000 is the failing XHR request domain. I have attached the screenshot.

How to ignore the XHR failing errors just like other browsers?

I am using '''Firefox Developer Edition''' Version: 1'''10.0b5 (64-bit)''' on '''M1 Mac''' running '''Ventura 13.1'''. I am building an webapp some XHR triggering in background but it is '''not necessary''' to run the application (running fine on other browsers). But on '''Firefox Developer Edition''', It shows a error window with the message and stops loading the application. '''Firefox can’t establish a connection to the server at localhost:4000.''' ''localhost:4000'' is the failing XHR request domain. I have attached the screenshot. How to ignore the XHR failing errors just like other browsers?
Attached screenshots

Chosen solution

It is resolved. Actually, It's a iFrame, The error appears inside the iframe that looks like an browser alert.

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Suluhisho teule

It is resolved. Actually, It's a iFrame, The error appears inside the iframe that looks like an browser alert.