`ensureImageHeaderHandle` fetched the caller-supplied `header_media_url`
server-side with no validation, so a template submit — an action any
authenticated member can perform — could reach loopback, RFC1918 and
cloud-metadata addresses, with the response status and content-type
echoed back through the thrown error.
Wire in the project's existing `isDeliverableUrl` guard, which the two
other outbound-fetch call sites (webhook delivery, automation
`send_webhook`) already use, and reuse their `redirect: 'manual'` +
timeout so a public URL can't 3xx-bounce to an internal one. The
rejection reuses the unreachable-host message verbatim so the failure
doesn't distinguish "blocked" from "down".
Addresses GHSA-6fr5-pxw7-r3xw.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Creating a template with an image header failed because the code sent
`example.header_url` — Meta only accepts a Resumable-Upload media handle
(`example.header_handle`) at creation time, never a plain URL.
- Resumable Upload: new `uploadResumableMedia` (meta-api) implements the
two-step `/{app_id}/uploads` flow → media handle. Needs META_APP_ID.
- Handle derivation: `ensureImageHeaderHandle` fetches the header image
(uploaded file OR pasted URL) and turns it into a handle before submit.
Wired into both the submit and edit (PATCH) routes with actionable 400s
(missing META_APP_ID, unreachable URL, wrong type, >5 MB). This fixes
BOTH the new upload path and the previously-broken manual-URL path.
- Template builder: add an image file upload (account-scoped chat-media
bucket via uploadAccountMedia) with preview + JPEG/PNG + 5 MB validation,
alongside the URL field.
- Send-time fix: an approved image template now sends the public
header_media_url as `link`; the resumable header_handle is NO LONGER
used as a send media id (it's invalid for sends and would fail).
- META_APP_ID documented as required for image-header templates.
Scope: image headers (the issue). Helper is generic for video/document.
typecheck/lint/build green; 421 tests (10 new).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
