What is a Server-Side Template Injection (SSTI) vulnerability?

A Server-Side Template Injection (SSTI) vulnerability arises from improperly handled user input in server-side templates. This type of vulnerability typically occurs when an application allows user input to be embedded directly into server-side templates without adequate validation or sanitization.

When the server processes these templates, it may inadvertently execute arbitrary code or scripts injected by an attacker, leading to various forms of exploitation. SSTI can enable attackers to access sensitive data, execute commands on the server, or manipulate the application’s behavior. Since the template is processed on the server, the impact of the vulnerability can be significant, as attackers can exploit it to gain unauthorized access to the server's environment, access files, or even escalate their privileges.

The other options do not accurately describe SSTI. For instance, the first option refers to client-side execution; however, SSTI vulnerabilities occur on the server-side. The third option incorrectly conflates SSTI with SQL injection, which pertains to database query vulnerabilities rather than template rendering vulnerabilities. Lastly, the fourth option mentions client-side storage of user credentials, which is not relevant to SSTI but rather a security concern in web application storage management. Thus, the correct understanding of SSTI highlights the importance of proper input handling in server-side rendering