SF_15.0 - https://www.progress.com/documentation/sitefinity-cms/configure-content-security-policy-header/

ProgramCSP.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;

using Progress.Sitefinity.AspNetCore;
using Progress.Sitefinity.AspNetCore.FormWidgets;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

//Add external source as trusted
builder.Services.AddSitefinity(x => x.CspOptions.CspDelegate = (cspDirectives, httpContext) =>
{
    cspDirectives.DefaultSrc += "*.example.com";
});

// Rest of the Program.cs file remains unchanged