Spring Security versions 5.2.x prior to 5.2.4 and 5.3.x prior to 5.3.2 contain a signature wrapping vulnerability during SAML response validation. When using the spring-security-saml2-service-provider component, a malicious user can carefully modify an otherwise valid SAML response and append an arbitrary assertion that Spring Security will accept as valid.
https://www.oracle.com/security-alerts/cpuoct2020.html
https://www.oracle.com/security-alerts/cpujan2021.html
https://www.oracle.com/security-alerts/cpuApr2021.html