Security Flaw: Insecure CSP Configuration Allows 'Unsafe-Inline' Styles in Backend Server

A security vulnerability has been identified in the backend server configuration, where the Content Security Policy (CSP) is weakened by the inclusion of `'unsafe-inline'` for style sources. This insecure setting, found in the `backend/src/server.js` file, creates a potential attack vector by permitting inline styles. While rated as a Low to Medium risk, this misconfiguration can be exploited in conjunction with other vulnerabilities, such as HTML injection, to manipulate page layouts or facilitate CSS-based data exfiltration attacks.

The specific code snippet reveals the CSP directive `styleSrc: ["'self'", "'unsafe-inline'"]`, which contradicts security best practices by allowing inline style execution. The presence of `'unsafe-inline'` significantly reduces the policy's effectiveness as a defense-in-depth measure. The vulnerability is isolated to this single line of code but represents a systemic failure in applying secure defaults for web application headers.

Remediation requires the immediate removal of the `'unsafe-inline'` directive. Developers must refactor the application to eliminate reliance on inline styles, migrating them to external stylesheets or securing them with cryptographic nonces or hashes as per the CSP specification. Failure to address this flaw leaves the application surface unnecessarily exposed to style-based attacks that could compound more severe security issues.