NextGEN Gallery version prior to 4.2.1 are vulnerable to authenticated SQL injection via the 'orderby' parameter on the REST API endpoints '/imagely/v1/galleries' and '/imagely/v1/albums'. The root cause is an insufficient sanitization function ('_clean_column()') in the data mapper layer that uses a character blacklist instead of a whitelist approach. This allows an authenticated attacker with the 'NextGEN Gallery overview' capability (assigned to the Administrator role by default) to inject arbitrary SQL into the 'ORDER BY' clause.