When working with Wordstat, a CAPTCHA (which is a picture and a field next to it where you enter the characters from the picture) can appear if you are accessing the service too frequently, or are located outside the Commonwealth of Independent States or Turkey, or if your browser cannot save the required cookie file. Yandex does not have the technical means to manually remove the CAPTCHA.
Cookies can be disrupted by your browser settings, extensions changing the content of a page, or your firewall.
To check that the required cookie file has been downloaded to your browser:
If fuid01 isn't shown, then that means cookies are blocked. Your cookies might be blocked by a firewall or extension that limits the display of page content (for example, AdBlock). Try to find and disable these blockers. As long as fuid01 doesn't appear on your computer, a CAPTCHA will be shown.
If you do see fuid01, but the CAPTCHA doesn't go away, then reduce the number of visits to the service. As a result, the CAPTCHA will disappear automatically.