# Verification or account merge preserves another actor's access

Registration, verification, email change, or federation merging transfers trust to an identity while retaining an unintended actor's usable credentials or session.

**Candidate CWE:** [CWE-287](https://cwe.mitre.org/data/definitions/287.html)

## Test hypothesis

In the replica, create an unverified password account for an owned test inbox in profile A. Complete the legitimate verified/federated signup for that inbox in profile B. Check whether A's prior password/session remains usable against the now-verified private account. Test a stale email-verification link after a second owned email change separately.

## Evidence required

Before/after internal account IDs, verification state, linked issuer/subject, origin of the retained credential, and controlled private access after the transition.

## Rule out false positives

Aliases intentionally identifying one account, explicit authenticated linking, a duplicate-registration error, or an unverified account that gains no new protected access is not account takeover.

## Playbook and command references

- [Authentication, recovery, federation, and session lifecycle](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/identity-session.html) — Test registration, recovery, identity changes, invitations, SSO enforcement, and deprovisioning as one account state machine.
- [OAuth, OIDC, and SAML: transaction binding and token trust](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/federation-token-trust.html) — Separate browser transaction binding, issuer trust, token purpose, and identity linking using controlled federation fixtures.

[Find the associated command snippets](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/commands.html?q=Authentication%2C%20recovery%2C%20federation%2C%20and%20session%20lifecycle)

## Referenced by these target playbooks

[Web & API](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/web-api.html) · [OSS & self-hosted](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/oss.html) · [Mobile](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/mobile.html) · [Desktop & extensions](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/desktop.html) · [Cloud & containers](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/cloud.html)

## Report checklist

- [ ] Capture the affected version, configuration, identities, and object ownership.
- [ ] Preserve a valid baseline and a negative control.
- [ ] Reproduce the forbidden data access, action, or state change on controlled fixtures.
- [ ] Explain the intended security rule and why the observed behavior violates it.
- [ ] State prerequisites, uncertainty, cleanup, and the smallest demonstrated impact.

## Conditional ATT&CK mapping

No direct ATT&CK mapping selected. Record the weakness and demonstrated impact without forcing an adversary-behavior classification. See the [mapping guide](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/attack.html).

## Primary references

- [OWASP Email Validation and Verification](https://cheatsheetseries.owasp.org/cheatsheets/Email_Validation_and_Verification_Cheat_Sheet.html)
- [OpenID Connect Core incorporating errata set 2](https://openid.net/specs/openid-connect-core-1_0.html)

[Back to the complete vulnerability catalog](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/vulnerabilities.html)