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THREAT OPS › Threat News › [GHSA] GHSA-63mc-hw7g-86rr (medium) — Phoenix: Presence keys colliding with `Object.prototype` members break existence checks

[GHSA] GHSA-63mc-hw7g-86rr (medium) — Phoenix: Presence keys colliding with `Object.prototype` members break existence checks

medgithub_advisoriesPublished 2026-09-03

GHSA-63mc-hw7g-86rr Severity: medium CVE: CVE-2026-56812

Phoenix: Presence keys colliding with `Object.prototype` members break existence checks

### Summary

The Phoenix JavaScript presence client (`assets/js/phoenix/presence.js`) tests whether a presence already exists using a bare truthiness check (`state[key]`) rather than an own-property check. Because applications commonly track presences u

MITRE ATT&CK techniques

JavaScriptT1059.007

Indicators of compromise

CVE-2026-56812cve

Original source: https://github.com/advisories/GHSA-63mc-hw7g-86rr