[🐛 Bug]: uploadFile command not available in Firefox since Selenium Docker image 4.31.0

What happened?

I'm encountering an issue with the uploadFile command when using Firefox in Docker Selenium images, starting from version 4.31.0.

When running WebdriverIO tests that rely on the uploadFile command with Firefox (inside the Docker Selenium container), the following error is returned:

Error: The uploadFile command is not available in firefox

This was working correctly in previous Docker image versions (e.g., 4.30.x). The issue does not occur with Chrome—only with Firefox.

I'm using the remote.uploadFile() WebDriver command to simulate file uploads in Firefox.

The same codebase works fine with Chrome.

It seems like a regression introduced in or after 4.31.0.

I opened an Issue in wdio repo webdriverio#14395

Command used to start Selenium Grid with Docker (or Kubernetes)

services:
    - name: selenium/standalone-firefox:latest
      alias: selenium

Relevant log output

[firefox 140.0.4 linux #0-3] Error: The uploadFile command is not available in firefox
[firefox 140.0.4 linux #0-3] Error: The uploadFile command is not available in firefox
[firefox 140.0.4 linux #0-3]     at Browser.uploadFile (/e2e/node_modules/webdriverio/build/node.js:119:11)
[firefox 140.0.4 linux #0-3]     at Browser.uploadFile2 (/e2e/node_modules/webdriverio/build/node.js:5611:39)
[firefox 140.0.4 linux #0-3]     at Browser.wrapCommandFn (/e2e/node_modules/@wdio/utils/build/index.js:978:32)

Operating System

linux

Docker Selenium version (image tag)

4.31.0 and above

Selenium Grid chart version (chart version)

No response

Start by reproducing remote.uploadFile() with Firefox in selenium/standalone-firefox:4.31.0 and compare it with a 4.30.x image, using the WebdriverIO issue linked in the report for context. Trace the Docker Selenium image changes around that version and verify completion by restoring uploadFile availability in Firefox without breaking the working Chrome path.