Conflict with Gboard on Firefox for Android: selecting a suggestion appends text instead of replacing it #3990

Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• The issue is not present after disabling uBO in the browser.
• I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• uBO is the only extension.
• uBO uses default lists and settings.
• using a new, unmodified browser profile.

Description

I’m experiencing a keyboard conflict with uBlock Origin on Firefox for Android.

A specific URL where the issue occurs.

No

Steps to Reproduce

1. Enable uBlock Origin on Firefox for Android.
2. Open any text input field (e.g., search bar, form field).
3. Type a partial word, for example "ca".
4. Gboard shows a suggestion, e.g., "Cagliari".
5. Tap the suggestion to accept it.

Expected behavior

The suggestion should replace the typed text (so "ca" becomes "Cagliari").

Troubleshooting information

· The issue does not occur in Firefox private/incognito mode (where extensions are disabled by default).
· Disabling uBlock Origin completely resolves the problem.
· The issue seems specific to the combination of uBlock Origin + Gboard + Firefox for Android. It does not happen with other keyboards (tested with SwiftKey) or with other browsers.

Environment:

· Device: Oppo A40m
· OS: ColorOS 15 (Android 15)
· Browser: Firefox for Android (latest version)
· Keyboard: Gboard (latest version)
· Extension: uBlock Origin (latest version)

Workaround found:
Replace uBlock Origin with an alternative blocker (e.g., AdGuard) or disable uBlock Origin entirely. The problem disappears as soon as uBlock Origin is turned off.