How Planes Fly: What They Taught You In School Was Wrong

One of the more important topics in web application security is the same
origin policy. It is a browser-based defense mechanism that makes it so that
certain conditions must be met before content (usually JavaScript) will be
run when served from a given website.

Rules

The rules are fairly simple: content wishing to run from a given location
must match all three of the following things:

• Domain

• Port

• Protocol

One way of remembering this is with the acronym DPP. So, the Same Origin
Policy (SOP) pertains to domain, port, and protocol (DPP). Or,
SOP = DPP.