An issue was discovered in the Quiz and Survey Master plugin before 7.0.1 for WordPress. It allows users to delete arbitrary files such as wp-config.php file, which could effectively take a site offline and allow an attacker to reinstall with a WordPress instance under their control. This occurred via qsm_remove_file_fd_question, which allowed unauthenticated deletions (even though it was only intended for a person to delete their own quiz-answer files).

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-35951
• https://wpscan.com/vulnerability/10348
• https://www.wordfence.com/blog/2020/08/critical-vulnerabilities-patched-in-quiz-and-survey-master-plugin/