CVE-2026-24523 is a vulnerability identified in the WP FullCalendar WordPress plugin developed by Marcus (aka @msykes). The issue allows an attacker without any authentication or user interaction to remotely retrieve embedded sensitive system information from affected installations running version 1.6 or earlier. The vulnerability is classified as an exposure of sensitive system information to an unauthorized control sphere, meaning that confidential data intended to be protected is accessible to unauthorized parties. The CVSS v3.1 base score is 7.5, indicating high severity, with the vector string AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, which translates to network attack vector, low attack complexity, no privileges required, no user interaction, unchanged scope, high impact on confidentiality, and no impact on integrity or availability. Although no known exploits are currently reported in the wild, the vulnerability's characteristics make it a significant risk for organizations using the affected plugin. The exposure of sensitive information can facilitate further attacks such as targeted phishing, privilege escalation, or lateral movement within networks. The lack of a patch link suggests that a fix may not yet be publicly available, increasing the urgency for temporary mitigations. The vulnerability affects WordPress sites that integrate the WP FullCalendar plugin, which is commonly used to display calendar events and schedules, making it relevant for organizations relying on this functionality.

For European organizations, the exposure of sensitive system information can lead to several adverse outcomes. Confidential data leakage may include configuration details, internal IP addresses, or other metadata that could be leveraged by attackers to craft more effective attacks. This can increase the risk of subsequent intrusions, data breaches, or service disruptions. Organizations in regulated sectors such as finance, healthcare, and government are particularly vulnerable due to the sensitivity of their data and the strict compliance requirements under GDPR and other regulations. The vulnerability's ease of exploitation without authentication means that any internet-facing WordPress site using the affected plugin is at risk, potentially leading to widespread impact. Additionally, the reputational damage and potential legal consequences from data exposure could be significant. The absence of known exploits in the wild currently provides a window for proactive defense, but this may change rapidly once the vulnerability becomes widely known.

1. Monitor official channels for a security patch release from the WP FullCalendar plugin developer and apply updates immediately upon availability. 2. In the absence of a patch, restrict access to the plugin's endpoints by implementing web application firewall (WAF) rules that block unauthorized requests targeting WP FullCalendar resources. 3. Employ IP whitelisting or VPN access controls to limit exposure of the WordPress administrative and plugin interfaces. 4. Conduct thorough audits of WordPress installations to identify the presence of the vulnerable plugin and assess exposure. 5. Disable or remove the WP FullCalendar plugin if it is not essential to reduce the attack surface. 6. Enhance monitoring and logging for unusual access patterns or data exfiltration attempts related to calendar functionalities. 7. Educate web administrators about the risks and ensure timely communication regarding plugin updates and security advisories. 8. Consider deploying Content Security Policy (CSP) and other browser security features to mitigate potential exploitation vectors.