update BFRAME?

Because there are multiple iframes in the interface and the internal selection is incorrect, I need to modify the selector, but it does not take effect
```
RecaptchaSolver.BFRAME = "iframe[src^='https://www.google.com/recaptcha/api2/bframe']:visible, iframe[src^='https://www.google.com/recaptcha/enterprise/bframe']:visible";

```

Locate the definition and usages of RecaptchaSolver.BFRAME, then inspect how the iframe selector is applied when multiple reCAPTCHA frames are present. Verify that the intended visible bframe is selected and that the updated selector takes effect; no test file is mentioned in the issue.

Written by the indexing model from the issue text.