Developers tasked with implementing SAML-based Single Sign-On (SSO) solutions face a challenging landscape due to the inherent complexity and vulnerability-prone nature of SAML, an XML-based authentication standard. The extensive attack surface is largely attributed to XML's cumbersome syntax and parsing difficulties, exacerbated by the complexity of the SAML specification and the involvement of multiple parties in the authentication process. Security vulnerabilities often arise from Service Providers (SPs) improperly validating SAML responses from Identity Providers (IdPs), leading to significant security risks if not properly addressed. Common vulnerabilities include XML Signature Wrapping (XSW) attacks, which exploit the separation between signature verification and payload processing, and replay attacks, which occur when SAML responses are captured and resent. To mitigate these risks, developers are advised to implement countermeasures such as disabling DTD processing, validating the SAML response schema, ensuring the intended recipient check, and rigorously validating every signature. Despite these precautions, building SAML SSO solutions in-house requires considerable investment and expertise, prompting developers to consider using third-party vendors like WorkOS that specialize in secure, high-performance SSO APIs. For those seeking alternative protocols, OpenID Connect is recommended as a more modern and safer option.