Hi Usman,
I guess your error isn't related to security but missing pre requisite of SAP UI5 library or incorrect version.
Error HTTP 404 means that a resource is not found, in case the library.js.
What is your HANA database revision?
Did you download manually the Web Editor or are using a version that came together with HANA database?
What is your UI5 library?
Regards, Fernando Da Rós