POST /api/v5/addons/upload/ fails with "backend write error" (CLI) / empty 503 (website)

Add-ons addons.mozilla.org
1

Uploading a new version of an existing add-on fails on the server side through both the CLI (web-ext sign) and the developer hub website. Nothing is wrong with the package locally (web-ext lint passes, ~14 MB).

  • Add-on name: Wallix Enterprise Vault
  • GUID: 73ad1dc7-ed8a-4610-a0af-957cfcb676a3
  • Type of submission: new version of an existing, listed add-on

Via web-ext sign — fails immediately on the upload POST, before validation starts:

[web-ext/lib/util/submit-addon.js][debug] POSTing URL: https://addons.mozilla.org/api/v5/addons/upload/
[web-ext/lib/util/temp-dir.js][debug] Removing temporary directory: /tmp/tmp-web-ext--42006-Rf56J4kBorfS
[web-ext/lib/program.js][error]
WebExtError: Upload failed: backend write error.
    at web-ext/lib/cmd/sign.js:101:13
    at process.processTicksAndRejections (node:internal/process/task_queues:104:5)
    at async Program.execute (web-ext/lib/program.js:270:7)
    at async web-ext/bin/web-ext.js:13:1

Reproduced identically with two separate web-ext installations (via npx, and via a global nvm install on Node v24.19.0), which rules out any client-side / tooling issue.

Via the developer hub website — uploading the same .zip manually fails as well, with:

Your add-on failed validation and generated 1 error.

  • Received an empty response from the server; status: 503

Endpoint: POST https://addons.mozilla.org/api/v5/addons/upload/

Steps to reproduce:

  1. Run web-ext sign --source-dir <dir> --channel=listed → fails immediately with “backend write error”.
  2. Upload the same .zip via the developer hub website → fails with an empty 503 response.
  3. Retried several times over the period below; same result both ways.

Details:

  • Add-on: Wallix Enterprise Vault (GUID 73ad1dc7-ed8a-4610-a0af-957cfcb676a3)
  • New version of an existing, listed add-on
  • Channel: listed
  • Package size: ~14 MB (well within limits)
  • web-ext lint passes locally with no errors
  • Both the CLI upload and the website upload fail server-side (backend write error / empty 503)
  • Time window of the failed attempts: from 09:15 to ~11:00 (Europe/Paris, CEST / UTC+2) on 2026-08-07, retried repeatedly throughout

Environment:

  • web-ext via both npx web-ext and global install (nvm, Node.js v24.19.0)

  • OS: Linux

    I try to sign my extension yesterday too, and same problem

2

Hi there and thanks fro reaching out!
I am unable to locate any Add-on with the name Wallix Enterprise Vault in addons.mozilla.org, or our database!

Could you please send me in private your email address to check your developer profile?

Thank you