CSRF refers to cross-site-request-forgery.
The error message "verification failed" means that the CSRF token sent with your form or request does not match the token stored on the server.
This could be due to missing tokens, incorrect context, cookie issues or misconfigured trust origins.
OWASP has done some great work on this.
Reminder: OWASP is the Open Worldwide Application Security Project, formerly known as the Open Web Application Security Project (name was updated in 2023).