In version 6.13.0 of LimeSurvey, any external user can cause a 500 error in the survey system by sending a malformed session cookie. Instead of displaying a generic error message, the system exposes internal backend information, including the use of the Yii framework, the MySQL/MariaDB database engine, the table name 'limesessions', primary keys, and fragments of the content that caused the conflict. This information can simplify the collection of data about the internal architecture of the application by an attacker.

Vulnerability in LimeSurvey 6.13.0 in the endpoint /optin that causes infinite HTTP redirects when accessed directly. This behavior can be exploited to generate a Denegation of Service (DoS attack), by exhausting server or client resources. The system is unable to break the redirect loop, which can cause service degradation or browser instability.

Vulnerability in LimeSurvey 6.13.0 in the endpoint /optout that causes infinite HTTP redirects when accessed directly. This behavior can be exploited to generate a Denegation of Service (DoS attack), by exhausting server or client resources. The system is unable to break the redirect loop, which can cause service degradation or browser instability.