A starting Content-Security-Policy
PlaintextBlocks inline script and restricts everything to the origin. Tighten from here rather than loosening from nothing.
Content-Security-Policy:
default-src 'self';
script-src 'self';
style-src 'self';
img-src 'self' data:;
object-src 'none';
base-uri 'self';
frame-ancestors 'none'