fix: Creating a session can delete another user's session

[mtrezza]

Issue

RestWrite.destroyDuplicatedSessions() runs the _Session deduplication delete without the if (this.response) return; guard that the other write-pipeline steps (runDatabaseOperation, runAfterSaveTrigger) use. On a non-master POST /classes/_Session create, handleSession() has already created the caller's own session and set this.response, but the dedup then issues a master-privileged delete keyed on the client-supplied user and installationId from the request body instead of the server-generated session data. As a result, creating a session can delete another user's _Session record for the supplied installationId.

Tasks

• Add tests

Summary by CodeRabbit

• Bug Fixes
  • Improved session handling to prevent valid user sessions from being deleted during duplicate-session cleanup.
  • Preserved existing session authentication when a new session is created with a matching installation identifier.
  • Added safeguards against unintended session changes after an earlier response has been generated.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 10e1b2e0-9290-4144-87c8-d6fbb4e832d0

📥 Commits

Reviewing files that changed from the base of the PR and between d76845f and 718b5aa.

📒 Files selected for processing (2)

• spec/ParseSession.spec.js
• src/RestWrite.js

---

📝 Walkthrough

Walkthrough

Session deduplication now skips deletion when an earlier response exists. A new test verifies that creating a session for another user with a shared installation ID preserves the original session record and authentication token.

Changes

Session deduplication

Layer / File(s)	Summary
Preserve existing sessions and validate authentication src/RestWrite.js, spec/ParseSession.spec.js	destroyDuplicatedSessions returns early when this.response is set, and the session test confirms the victim’s session remains present and can authenticate requests.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• parse-community/parse-server#10195: Both changes address _Session handling and client-supplied session fields.
• parse-community/parse-server#10313: Both changes cover session deduplication behavior involving installation IDs and users.
• parse-community/parse-server#10319: Both changes modify session deduplication control flow in RestWrite.js.

🚥 Pre-merge checks | ✅ 7

✅ Passed checks (7 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title matches the fix prefix requirement and accurately summarizes the session deletion issue.
Description check	✅ Passed	The description includes an Issue section and completed Tasks, but it omits the template's Approach section.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Security Check	✅ Passed	The patch removes a cross-user session-deletion path by skipping dedup after _Session responses exist, and the tests verify user-supplied session fields are ignored.
Engage In Review Feedback	✅ Passed	GitHub shows “No reviews” on PR #10582, so there were no feedback comments to ignore. citeturn3view0

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.69%. Comparing base (d76845f) to head (718b5aa).

Additional details and impacted files

@@            Coverage Diff             @@
##            alpha   #10582      +/-   ##
==========================================
- Coverage   92.70%   92.69%   -0.01%     
==========================================
  Files         193      193              
  Lines       17025    17027       +2     
  Branches      248      248              
==========================================
+ Hits        15783    15784       +1     
- Misses       1221     1222       +1     
  Partials       21       21              

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[mtrezza]

@coderabbitai full review

[coderabbitai]

✅ Action performed

Full review finished.

[parseplatformorg]

🎉 This change has been released in version 9.10.1-alpha.2