same-origin-policy security-model cors cross-origin-isolation web-fundamentals

Same-Origin Policy foundations shape web security

Origin (scheme + host + port) is the fundamental security boundary; cross-origin resource loading permits execution but blocks read access, creating leak vectors through side effects.

Summary

Misunderstanding origin scope causes cache-poisoning, CSRF, and unintended data leaks when embedding third-party scripts or iframes. Developers need precise mental models to avoid cross-site script inclusion vulnerabilities.

Why it matters

Implementation verdict

This is foundational reference material, not a tool or library. Use it to audit your iframe/popup interactions and HTTP request handling. Requires reviewing your cross-origin postMessage calls and CORS configurations against the documented corner cases (window.length reads, location.replace navigation tricks).

Sources

1.An origin is usually a tuple of a scheme, a host and a port of a URL
2.cross-origin resources that are loaded into the current document (e.g., scripts, images) can be used (e.g., executed or displayed) but not properly read
3.This can lead to unintended leaks, called Cross-Site Script Inclusions
4.A Site is a combination of a scheme and a host's registerable domain
5.Cross-Origin Isolation is a newer security boundary, that was created as a reaction to two noteworthy attack groups

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