CVE-2025-68979 is an authorization bypass vulnerability identified in the SimpleCalendar Google Calendar Events plugin, affecting all versions up to and including 3.5.9. The root cause is an incorrectly configured access control mechanism that relies on a user-controlled key to authorize access to calendar event data. An attacker with low privileges (PR:L) can exploit this flaw remotely (AV:N) without requiring user interaction (UI:N) to gain unauthorized access to sensitive calendar events, thereby compromising confidentiality and integrity. The vulnerability does not affect availability. The CVSS v3.1 base score is 8.1 (high), reflecting the ease of exploitation and the significant impact on data confidentiality and integrity. Although no public exploits are known yet, the vulnerability's nature suggests it could be leveraged to access or manipulate calendar events, potentially exposing sensitive organizational information or enabling further attacks. The issue affects organizations using the SimpleCalendar plugin integrated with Google Calendar, which is commonly used for scheduling and event management. The vulnerability was published on December 30, 2025, with no patches currently available, emphasizing the need for immediate attention to access control policies and monitoring.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of calendar event data, which often contains sensitive business information, meeting details, and personal data protected under GDPR. Unauthorized access could lead to data leakage, espionage, or manipulation of event information, disrupting business operations and damaging trust. Organizations heavily reliant on Google Workspace and third-party calendar integrations are particularly vulnerable. The breach of calendar data could also facilitate social engineering or spear-phishing attacks by exposing meeting participants and schedules. Given the network-based attack vector and lack of required user interaction, the threat can be exploited remotely and stealthily, increasing the risk of widespread impact across multiple departments or subsidiaries within European enterprises.

1. Immediately audit and tighten access control configurations within the SimpleCalendar plugin settings to restrict user-controlled keys and ensure proper authorization checks are enforced. 2. Monitor logs and access patterns for unusual or unauthorized access attempts to calendar event data. 3. Implement network-level controls such as IP whitelisting or VPN requirements for accessing calendar management interfaces. 4. Educate administrators and users about the risks of sharing calendar links or keys and enforce strict policies on calendar sharing. 5. Apply any vendor-released patches or updates as soon as they become available. 6. Consider temporarily disabling the SimpleCalendar Google Calendar Events plugin if feasible until a patch is released. 7. Use multi-factor authentication (MFA) for accounts managing calendar events to reduce the risk of credential compromise. 8. Engage with the vendor or community for updates and potential workarounds to mitigate the vulnerability.