Session Fixation Vulnerability in arubis/sample_rails_app Exposes Authentication Flaw

A critical session fixation vulnerability has been identified in the arubis/sample_rails_app repository, exposing a fundamental flaw in its authentication mechanism. The automated security scanner RSOLV flagged a single, high-confidence instance of Broken Authentication (CWE-384) in the master branch, directly linked to the OWASP Top 10 category for Identification and Authentication Failures. The core issue resides in the `app/helpers/sessions_helper.rb` file, where the code fails to regenerate the session ID after a user logs in, creating a persistent risk of session hijacking.

The vulnerability is pinpointed to line 5 of the sessions helper, where `session[:user_id] = user.id` is set without invalidating the previous session. This omission allows an attacker who can fixate a session identifier—for instance, by tricking a user into using a known session ID—to potentially gain unauthorized access to that user's account after they authenticate. While classified with MEDIUM severity and 80% confidence, the flaw represents a direct pathway for compromising user accounts and application security.

This finding places immediate scrutiny on the repository's security posture and development practices. For the maintainers of the sample_rails_app, the automated recommendation is a mandatory code review and remediation adhering to security best practices, specifically implementing session regeneration upon login. The presence of such a basic yet impactful vulnerability in a public repository branch underscores the persistent risks in web application security, even in sample or educational codebases, and signals a need for enhanced security scanning and review protocols.