Cross-Site Scripting (XSS) is a web security vulnerability that enables attackers to inject malicious scripts into web pages viewed by users. When a user visits an affected web page, the malicious code runs on their browser, potentially allowing the attacker to steal sensitive data, hijack user sessions, or deface websites. XSS attacks can be categorized into three types: stored, reflected, and DOM-based. Preventing XSS attacks involves validating user input, escaping untrusted data, and following secure coding practices for web applications.

Structured Query Language (SQL) Injection is a web security vulnerability that allows attackers to interfere with the SQL queries performed by a web application. Attackers can exploit this vulnerability to view, modify, or delete data stored in a database, depending on their level of access. In some cases, they may even gain administrative access to the system. Preventing SQL Injection attacks requires the use of parameterized queries, input validation, and least privilege access control, among other secure coding practices.

Cross-Site Request Forgery (CSRF) is a web security vulnerability that forces a user's browser to perform unwanted actions on a web application in which they are authenticated. CSRF attacks exploit the trust that web applications have for authenticated users and can result in unauthorized data modification, unauthorized transaction execution, or even account takeover. Defending against CSRF attacks involves implementing proper anti-CSRF tokens, verifying the origin of requests, and following the principle of least privilege.

Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols designed to provide secure communication over the internet. They protect data transmitted between a user's web browser and a web server from eavesdropping, tampering, and message forgery. TLS and SSL ensure data integrity, confidentiality, and authentication in web applications. Ensuring web security requires proper implementation and configuration of TLS/SSL, including selecting strong cipher suites and monitoring for emerging vulnerabilities.

Content Security Policy (CSP) is a security feature that helps prevent cross-site scripting (XSS) and other code injection attacks. It allows web developers to define a whitelist of trusted sources for content, such as scripts, images, and styles. When implemented correctly, CSP can effectively block unauthorized execution of inline scripts and external resources, reducing the risk of XSS attacks and other injection-based vulnerabilities. Implementing a strong CSP in web applications involves defining strict policies, ensuring proper server configuration, and continuously monitoring for violations.

The Same-Origin Policy (SOP) is a crucial web security concept implemented by browsers to prevent web pages from different domains from sharing data or resource access. Through this policy, web pages from one site can't interact with data or resources from another site unless both pages share the same origin - same domain, same protocol (HTTP or HTTPS), and same port. SOP helps mitigate various security risks, such as unauthorized access to sensitive user information, by confining web pages within a security sandbox and preventing unauthorized access to potentially sensitive data.

The Content Security Policy (CSP) Header is a security measure to prevent Cross-Site Scripting (XSS), clickjacking, and other code injection attacks by specifying allowed sources of content for a web page. When implemented, the web server sends an HTTP response header with a policy to the browser, which enforces it. The policy dictates authorized sources for resources like images, scripts, and styles, helping prevent various attacks by limiting where these resources can be loaded from. If an attacker tries to inject malicious content from an unauthorized source, the browser will not load it, protecting the user from potential security threats.

HTTP Strict Transport Security (HSTS) is a security mechanism that enforces the use of HTTPS, ensuring data encryption and secure network communication in web applications. When enabled on a web server, the server sends an HSTS header in the HTTP response, instructing the browser to establish HTTPS connections only to that specific domain. This reduces the risk of man-in-the-middle attacks, as any attempt to downgrade the connection to HTTP or establish a connection with an invalid certificate will be blocked by the browser.

Clickjacking Defense refers to techniques used to protect web applications from clickjacking attacks, in which an attacker tricks a user into clicking a hidden element by overlaying it on top of what appears to be a legitimate element on the site. This deceptive action often leads to unintended consequences like unauthorized actions, revealing sensitive information, or even downloading malware. Common defensive mechanisms against clickjacking include using the 'X-Frame-Options' HTTP header to limit or deny framing, implementing Framebusting JavaScript, or using a Content Security Policy header to control the origins allowed to frame the content.

Secure Cookie Handling refers to best practices and techniques employed when using cookies to store and transmit sensitive information, such as authentication or session data. Common practices include setting the 'secure' attribute for cookies, ensuring they are transmitted over HTTPS only and preventing potential interception over unencrypted HTTP connections. Additionally, the 'HttpOnly' attribute should be set to limit client-side script access to cookies, reducing the risk of unauthorized access through Cross-Site Scripting (XSS) attacks. It is also recommended to set an appropriate expiration time for cookies, which helps limit the potential exposure of any compromised data.