Firefox extension autofill broken — InputJsonDeserializationFailed

Question

Since updating to 1Password 8.12.5 on Linux, the autofill feature no longer works in Firefox-based browsers (Firefox and Zen Browser). The same extension version (8.12.4.46) works correctly in Chromium. Copying passwords from the extension popup works fine — only the fill/autofill operation is broken.

Environment:

OS: Arch Linux (kernel 6.19.6)
1Password app: 8.12.5 (also tested with beta 8.12.6-35 — same issue)
1Password extension: 8.12.4.46 (latest on AMO)
Firefox: 148.0 (also tested with 147.0.4 — same issue)
Chromium: autofill works with the same extension version and app

Steps to reproduce:

Open any login page in Firefox
Focus on a username/password input field
The 1Password inline menu appears and shows matching logins — this works
Click on a login to fill — nothing happens

Filling via the toolbar popup and keyboard shortcut also does nothing. Copying a password works fine.

Error from about:debugging → 1Password → Inspect:

Uncaught (in promise) Error: ⛔ Core error code: InputJsonDeserializationFailed

  sendCoreMessage background.js:108

  nextFill background.js:108

What I've tested:

Test	Result
Chromium + same extension + same app	Fill works
Firefox 148 / 147.0.4	InputJsonDeserializationFailed
1Password beta 8.12.6-35	InputJsonDeserializationFailed
X11 instead of Wayland	InputJsonDeserializationFailed
Copy password from extension	Works

The Firefox extension's fill request (nextFill → sendCoreMessage) is rejected by BrowserSupport with InputJsonDeserializationFailed. The same extension version works in Chromium, so the issue is in the Firefox-specific fill payload. This is a regression from the 8.12.2 → 8.12.5 app update (downgrading is blocked by database migration).

pdesoyres · Answer

After digging a bit :

The error is not raised on every web site:

- error occurs on clever cloud console (https://api.clever-cloud.com/v2/sessions/login)
- error doesn't occur on github.com

What I can see is that in the next-fill event JSON data, I have a null frame on clever cloud console:

{
  "name": "next-fill",
  "data": {
    "collectedPageDetails": {
      "unparsedUrl": "https://api.clever-cloud.com/v2/sessions/login?fromAuthorize=true&partner_id=01907806-284e-1b4d-029a-20b9ebfcb8c0",
      "title": "Log in · Clever Cloud",
      "frames": [
        {
          "fields": [
            {
              "formOpid": 0,
              "htmlId": "login-email",
              "htmlName": "email",
              "htmlClass": "form-control",
              "isActive": true,
              "opid": 0,
              "tabIndex": 1,
              "type": "email",
              "dataAttributes": {},
              "label": "EMAIL ADDRESS",
              "labelBefore": "Email address"
            },
            {
              "formOpid": 0,
              "htmlId": "login-pwd",
              "htmlName": "pass",
              "htmlClass": "form-control",
              "maxLength": 4096,
              "minLength": 6,
              "opid": 1,
              "tabIndex": 2,
              "type": "password",
              "dataAttributes": {},
              "label": "PASSWORD",
              "labelBefore": "Password Lost password?"
            },
            {
              "formOpid": 0,
              "htmlClass": "btn-signup btn-github",
              "opid": 2,
              "tabIndex": 3,
              "type": "submit",
              "value": "LOG IN",
              "dataAttributes": {}
            }
          ],
          "forms": [
            {
              "htmlAction": "https://api.clever-cloud.com/v2/sessions/login",
              "htmlMethod": "post",
              "opid": 0,
              "textContent": "Email Login EMAIL ADDRESS PASSWORD LOST PASSWORD? LOG IN OR GitHub Login CONNECT"
            }
          ],
          "origin": {
            "type": "url",
            "content": {
              "origin": "https://api.clever-cloud.com",
              "pathName": "/v2/sessions/login"
            }
          },
          "title": "Log in · Clever Cloud",
          "uuid": "ka3l3x"
        },
        null
      ]
    }
  }
}

if i dynamically drop this null frame, autofill works.

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