Mozilla confirmed a recaptcha issue in the organization's Firefox web browser yesterday evening.

Affected Firefox users see a spinning animation when they try to solve the captcha, which means that they are unable to do so. The result is that they cannot access the website or service. A workaround is available.

The issue affects all major versions of Firefox for Windows that are supported  by Mozilla as well as older versions. This includes Firefox 125, the current stable version of Firefox, the development versions 126 and 127, and also Firefox ESR 115.

Mozilla says that the issue is not caused by changes that it made to Firefox. Instead, it believes that Google is the culprit and it makes the following points to back this up:

• The issue affects new and old Firefox installations alike. It affects Firefox ESR, Firefox Stable, and also Firefox releases that were released last year and are no longer supported.
• Changing the user agent to Firefox for Linux or Chrome for Windows makes the captchas work again.
• Changing the user agent of Chrome to Firefox for Windows breaks the captchas in Chrome as well.

Workaround for the Firefox captcha issue

Firefox users who run into the issue may resolve it in the following way:

1. Type about:config in the Firefox address bar.
2. Search for general.useragent.override.
3. Switch to String and activate the add-icon.
4. Copy and paste the following string into the field: Mozilla/5.0 (X11; Linux x86_64; rv:125.0) Gecko/20100101 Firefox/125.0.
5. Click on the edit icon next to the line to save the change.

Firefox identifies as Firefox for Linux now. You may also use a different user agent, e.g., that for Chrome for Windows.

Note: you may want to delete the entry again once the issue is fixed.

Closing Words

Provided that Mozilla's assessment of Google being the culprit is correct, it highlights a major issue. Google, being also one of the main competitors of Mozilla, has also control over large popular Internet services.

This includes websites such as Google Search, Gmail, or YouTube, but also behind-the-scenes services such as recaptcha. Even unintentional changes may have severe consequences for Firefox and other competing browsers, especially if they do not use Chromium as the core.

Check out the bug report for additional information about the issue and fixes.

Do you use Firefox? Have you experienced issues with captchas recently?