The Quiz and Survey Master (QSM) plugin for WordPress is vulnerable to SQL Injection via the 'merged_question' parameter in all versions up to, and including, 10.3.5. This is due to insufficient sanitization of user-supplied input before being used in a SQL query. The sanitize_text_field() function applied to the merged_question parameter does not prevent SQL metacharacters like ), OR, AND, and # from being included in the value, which is then directly concatenated into a SQL IN() clause without using $wpdb->prepare() or casting values to integers. This makes it possible for authenticated attackers, with Contributor-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.