JavaScript Security

  1. Defensive Coding and Mitigation Strategies
    1. Input Validation and Sanitization
      1. Distinguishing Validation from Sanitization
        1. Purpose of Validation
          1. Purpose of Sanitization
            1. Complementary Approaches
            2. Allow-listing vs. Deny-listing
              1. Advantages of Allow-listing
                1. Pitfalls of Deny-listing
                  1. Hybrid Approaches
                  2. Server-Side vs. Client-Side Validation
                    1. Importance of Server-Side Validation
                      1. Role of Client-Side Validation
                        1. Defense in Depth
                        2. Using Sanitization Libraries
                          1. DOMPurify
                            1. js-xss
                              1. Integration Best Practices
                                1. Library Selection Criteria
                                2. Regular Expression Security
                                  1. ReDoS (Regular Expression Denial of Service)
                                    1. Safe Pattern Design
                                      1. Performance Considerations
                                    2. Output Encoding
                                      1. The Principle of Contextual Encoding
                                        1. Encoding Based on Output Context
                                          1. Context-Aware Escaping
                                          2. Encoding for Different Contexts
                                            1. HTML Body
                                              1. HTML Attributes
                                                1. JavaScript Strings
                                                  1. CSS Values
                                                    1. URL Components
                                                      1. JSON Data
                                                      2. Dangers of Improper Encoding
                                                        1. Double Encoding
                                                          1. Encoding Omissions
                                                            1. Character Set Issues
                                                            2. Encoding Libraries and Functions
                                                              1. Native Browser APIs
                                                                1. Third-Party Libraries
                                                                  1. Framework-Specific Solutions
                                                                2. Secure DOM Manipulation
                                                                  1. Avoiding Insecure Methods
                                                                    1. innerHTML vs. textContent
                                                                      1. Risks of document.write()
                                                                        1. Dangers of eval() and Similar Functions
                                                                          1. Function Constructor Risks
                                                                          2. Using Trusted Types
                                                                            1. Concept and Implementation
                                                                              1. Enforcing Trusted Types in Applications
                                                                                1. Policy Configuration
                                                                                2. Safe Sink Usage
                                                                                  1. Identifying Safe and Unsafe Sinks
                                                                                    1. Best Practices for DOM Updates
                                                                                      1. Event Handler Security
                                                                                      2. Template Security
                                                                                        1. Client-Side Template Engines
                                                                                          1. Template Injection Prevention
                                                                                            1. Secure Template Practices

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                                                                                        2. Core Client-Side Vulnerabilities

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                                                                                        4. Browser Security Policies and Features