If you try to import huge URLs in single URL list on the Web Security Service(WSS) portal
you cannot save and "An Unknown server error occurred" is displayed.
An unknown server error has occurred
It is necessary to transfer the updated data to the cloud side when saving URL list.
Hit the timeout limit of 60 seconds because there is too much transfer data.
The timeout value is a specification of WSS portal.
It depends on the user's network environment (network speed) but the recommended value for the number of URLs to import in single URL list is 1000-1500.
The result to import URL list around 1000-1500 is consistently positive.