CVE-2017-20273: SQL Injection in Joomla Event Registration Pro Calendar 4.1.3

Technical summary

The vulnerability exists in the id parameter handling within the com_registrationpro component's category view (index.php?option=com_registrationpro&view=category&id=...). User-supplied input is not properly sanitized before being incorporated into SQL queries, enabling an unauthenticated attacker to break out of the intended query context and execute arbitrary SQL commands. The flaw is classified as CWE-89 (SQL Injection) and carries a CVSS v3.1 score of 8.2 (HIGH severity), reflecting the combination of network-based exploitability, lack of authentication requirements, and high impact on data confidentiality.

Business impact

A successful exploitation could expose customer contact information, registration details, event attendance records, and other sensitive data stored in the Joomla database. For organizations running this plugin, the primary risk is unauthorized data disclosure that may violate privacy obligations or regulatory requirements. The attacker gains read access to database contents without audit trail detection, creating compliance and reputational risks. No direct data modification or denial of service is possible through this vector alone, but data theft at scale is straightforward.

Affected systems

Joomla Event Registration Pro Calendar version 4.1.3 is confirmed vulnerable. Users should verify whether earlier or later versions are affected by consulting the vendor advisory directly. The vulnerability applies to any installation where the registration pro component is active and accessible via the web interface.

Exploitability

This is a straightforward, unauthenticated SQL injection requiring only a specially crafted GET request. No authentication, user interaction, or special conditions are required. Attackers need basic SQL knowledge and network access to the affected Joomla instance. The attack surface is wide because the vulnerable parameter is exposed on a public-facing web endpoint. No known public exploit code has been designated for active exploitation campaigns as of the current date.

Remediation

Organizations should apply the security patch provided by the vendor immediately. Until patching is possible, restrict access to the affected Joomla instance at the network level or disable the registration pro component if it is not in active use. Review database access logs and logs from the vulnerable endpoint to identify whether exploitation has already occurred.

Patch guidance

Consult the official Joomla and Event Registration Pro vendor advisories for the specific patched version that addresses CVE-2017-20273. Apply updates in a controlled manner—test in a non-production environment first to verify compatibility with custom extensions and configurations. Verify against the vendor advisory that the patch version you deploy fully remediates this SQL injection flaw before rolling out to production.

Detection guidance

Monitor web server logs for GET requests to index.php containing option=com_registrationpro&view=category&id with suspicious characters such as single quotes, SQL keywords (SELECT, UNION, OR), or encoded payloads. Database query logs and slow-query logs may reveal anomalous SQL statements if exploitation is occurring. Intrusion detection systems with SQL injection signatures should flag malicious payloads in the id parameter. Baseline normal traffic patterns for this endpoint and alert on deviations.

Why prioritize this

Although not yet listed on CISA's Known Exploited Vulnerabilities catalog, the HIGH CVSS score (8.2) combined with unauthenticated, network-based exploitability makes this a critical patching priority. Organizations should treat this as urgent and deploy fixes within days rather than weeks, especially for internet-facing instances. The ease of exploitation and potential for large-scale data exposure justify elevated priority in patch management workflows.

Risk score, explained

The CVSS v3.1 score of 8.2 reflects: (1) Network-based attack vector requiring no special network position; (2) Low attack complexity with no authentication or user interaction needed; (3) High confidentiality impact due to unrestricted database read access; (4) Limited integrity impact (SQL injection can modify data but that is not the primary attack path here); and (5) No availability impact. The score emphasizes that data exfiltration is the dominant threat, warranting urgent remediation.

Frequently asked questions