What this check examines
These questions examine what the browser actually does with a document, rather than how a fragment happens to look. They connect parsing, navigation, and isolation to decisions you will encounter when embedding a widget or maintaining a learning playground. Read the stated conditions carefully: a security property can change when one permission is added.
Before answering, review the iframe and troubleshooting lessons. Predict which document owns an operation, which origin the browser assigns, and which part of the system is trusted to make a decision. Avoid answers that treat escaping, validation, and sandboxing as interchangeable. They address different boundaries.
After the quiz, draw a small diagram of a parent page and an embedded document. Mark where learner code executes and where the site reads account data. Explain why allowing scripts in a sandbox is different from allowing same-origin access. Then inspect an actual iframe element in developer tools and compare its permissions with your diagram. The score confirms your selected answers; the inspection exercise tests whether you can apply the ideas.
Reason through the choices
Turn the result into practice
Revisit each explanation you missed. Write a small counterexample that demonstrates why the tempting answer fails, then compare the source, parsed tree, and behavior. You can revise your answers and check again; scores stay on this device when storage is available.
Review the related lesson · Inspect a document · Try a coding challenge