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Bug Chain

NoteShare — Change email

Scenario

NoteShare lets users leave HTML notes and change account email via a bare POST. There is no CSRF token on email updates, and notes render unsanitised. End-to-end, redirect a victim's login email to an address you control.

Your approach

  1. Explore note creation and the account email change form.
  2. Either forge a cross-site POST to the email endpoint or store XSS that performs it.
  3. Change the victim email to your attacker domain.
  4. Confirm the lab registers a full chain takeover.
  5. Submit the chain ATO flag.
1 Plant a note
2 Force email change
3 Claim the flag

Self-service email update. Inspect the form — is anything stopping a cross-site POST?

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