Encryption plays a crucial role in enhancing data security by converting sensitive information into unreadable code, ensuring that only authorized parties with the decryption key can access the data. This protects data at rest (stored data) and data in transit (data being transmitted) from unauthorized access and breaches. Encryption helps in maintaining data confidentiality, integrity, and authenticity, thus safeguarding sensitive information from hackers, insider threats, and other malicious actors.

Potential Vulnerabilities and Mitigations:
1. Key Management: Poor key management can lead to compromised keys, making encrypted data vulnerable. Implement strong key management practices, such as regular key rotation, secure key storage, and access controls.
2. Algorithm Weaknesses: Using outdated or weak encryption algorithms can expose data to brute force attacks. Use strong, modern encryption standards like AES-256 and RSA-2048.
3. Implementation Flaws: Incorrect implementation of encryption can introduce vulnerabilities. Follow best practices and guidelines, and regularly audit encryption implementations.
4. Insider Threats: Authorized personnel might misuse access to encryption keys. Implement strict access controls and monitoring to mitigate this risk.
5. End-to-End Encryption: Ensure end-to-end encryption to protect data throughout its lifecycle, preventing exposure at any transmission point.

By addressing these vulnerabilities and implementing robust encryption strategies, businesses can significantly enhance their data security posture.

To secure a web application against SQL injection and cross-site scripting (XSS), follow these best practices:

SQL Injection Prevention:
1. Parameterized Queries: Utilize prepared statements with parameters to separate SQL code from data.
2. ORM (Object-Relational Mapping): Implement an ORM library to abstract and manage database queries securely.
3. Input Validation: Validate and sanitize all user inputs to ensure they conform to expected formats.
4. Least Privilege Principle: Limit database account privileges to only what is necessary for their functions.
5. Stored Procedures: Use stored procedures to encapsulate SQL logic and minimize injection risks.

XSS Prevention:
1. Output Encoding: Encode data before displaying it in the browser to prevent the execution of malicious scripts.
2. Content Security Policy (CSP): Implement CSP headers to restrict the sources from which scripts can be loaded.
3. Input Validation: Validate and sanitize user inputs, especially those rendered in the browser.
4. HTTPOnly and Secure Cookies: Use these attributes to prevent client-side access to cookies and ensure they are sent over secure channels.
5. Framework Security Features: Use the built-in security features of web frameworks to help mitigate XSS vulnerabilities.

By consistently applying these best practices, you can significantly reduce the risk of SQL injection and XSS in your web applications.