Parse Server is an open-source backend framework that runs on Node.js and commonly uses MongoDB as its database. The MongoDB explain() method provides detailed insights into query execution plans, including index usage, collection scanning behavior, and performance metrics. Prior to parse-server version 8.5.0-alpha.5, any client could invoke explain queries without authentication or requiring the master key. This vulnerability (CVE-2025-64502) results in the insertion of sensitive information into sent data, specifically exposing database schema details such as field names, index configurations, and query execution statistics. Such information disclosure can aid attackers in understanding the database structure and identifying potential performance bottlenecks or attack vectors, such as query optimization abuse or denial of service via expensive queries. The vulnerability is classified under CWE-201 (Insertion of Sensitive Information Into Sent Data). In version 8.5.0-alpha.5, a new configuration option databaseOptions.allowPublicExplain was introduced to restrict explain queries to requests authenticated with the master key. However, this option currently defaults to true to maintain backward compatibility, with a security warning logged if not explicitly set or set to true. A future major release will change the default to false, enforcing stricter access control. Until then, organizations are recommended to implement middleware to block explain queries from unauthorized clients or monitor and alert on such usage. The CVSS 4.0 vector indicates network attack vector, low attack complexity, no privileges or user interaction required, and low scope impact, resulting in a medium severity score of 6.9. No known exploits have been reported in the wild, but the exposure of sensitive backend information poses a significant risk to confidentiality and could facilitate further attacks.

For European organizations using parse-server versions prior to 8.5.0-alpha.5, this vulnerability can lead to unauthorized disclosure of sensitive backend database schema information. Exposure of field names, index configurations, and query execution plans can enable attackers to craft targeted attacks such as query performance exploitation, denial of service via expensive queries, or further database compromise. This undermines the confidentiality of backend data structures and may indirectly affect data integrity and availability if attackers exploit performance weaknesses. Organizations relying on parse-server for critical applications or handling sensitive data are at risk of information leakage that could facilitate more severe attacks. The vulnerability requires no authentication or user interaction, increasing the risk of automated scanning and exploitation attempts. Although no exploits are currently known in the wild, the widespread use of parse-server in various industries across Europe, including technology startups, e-commerce, and mobile backend services, means the potential impact is broad. Failure to mitigate this vulnerability could lead to reputational damage, regulatory non-compliance (e.g., GDPR concerns about data protection), and operational disruptions.

European organizations should prioritize upgrading parse-server to version 8.5.0-alpha.5 or later, where the databaseOptions.allowPublicExplain configuration option is available. They should explicitly set this option to false to restrict explain queries to requests authenticated with the master key, thereby preventing unauthorized access. Until upgrading is feasible, implement custom middleware to detect and block explain queries from clients lacking master key authentication. Additionally, enable detailed logging and monitoring of explain query usage to detect suspicious activity and trigger alerts. Conduct regular audits of backend access patterns to identify potential abuse. Network-level controls such as firewall rules or API gateways can be configured to restrict access to parse-server endpoints from untrusted sources. Educate development and operations teams about the risks of exposing explain queries publicly and enforce secure configuration management practices. Finally, prepare for the upcoming major release where the default will change to disallow public explain queries, ensuring compatibility and security readiness.