404 Monitor detects errors in Captcha

Could you provide some examples of URLs showing up in 404 Monitor?

https://mywebsite.com/wp-content/plugins/si-contact-form/captcha-secureimage/securimage_show.php?ctf_sm_captcha=1&prefix=kTik4INMi1Qqw50Q

Google’s image search engine is trying to spider your captcha images, but it can’t find them because the captcha changes every time, hence the 404 errors.

To stop Google from spidering your captcha images and other plugin files, use SEO Ultimate’s File Editor to add this to your robots.txt file:

User-agent: *
Disallow: /wp-content/plugins/

Then check the “enable this custom robots.txt file” checkbox and click “Save Changes” to activate the rule.

To stop 404 Monitor from tracking your captcha 404s, add this to the “URLs to Ignore” textbox on the “Settings” tab:

*/si-contact-form/captcha-secureimage/securimage_show.php?*

what can it cause if I just leave it like that?