Exakat is a static analysis tool for PHP designed to improve code quality and ensure best practices in PHP projects. Like Psalm, it focuses on analyzing PHP code, but it offers unique features and analyses to help developers identify issues and make their applications more efficient and secure.

Here are some of Exakat’s main features:

1. Code Quality and Best Practices: Exakat analyzes code based on recommended PHP best practices and ensures it adheres to modern standards.
2. Security Analysis: The tool identifies potential security vulnerabilities in the code, such as SQL injections, cross-site scripting (XSS), or other weaknesses.
3. Compatibility Checks: Exakat checks if the PHP code is compatible with different PHP versions, which is especially useful when upgrading to a newer PHP version.
4. Dead Code Detection: It detects unused variables, methods, or classes that can be removed to make the code cleaner and easier to maintain.
5. Documentation Analysis: It verifies whether the code is well-documented and if the documentation matches the actual code.
6. Reporting: Exakat generates detailed reports on code health, including metrics on code quality, security vulnerabilities, and areas for improvement.

Exakat can be used as a standalone tool or integrated into a Continuous Integration (CI) pipeline to ensure code is continuously checked for quality and security. It's a versatile tool for PHP developers who want to maintain high standards for their code.

A web application firewall (WAF) is a security solution that has been specially developed to protect web applications. It monitors traffic between web browsers and web applications to detect and block potentially harmful or unwanted activity. Essentially, a WAF acts as a shield that protects web applications from a variety of attacks, including

1. SQL injection: an attack technique where attackers inject malicious SQL queries to access or manipulate the database.
2. Cross-site scripting (XSS): An attack method where attackers inject scripts into websites to compromise users, such as by stealing session cookies or performing malicious actions on the user's behalf.
3. Cross-site request forgery (CSRF): An attack in which an attacker makes a fraudulent request on behalf of an authenticated user to perform unwanted actions.
4. Brute force attacks: Repeated attempts to log into a system using stolen or guessed credentials.
5. Distributed Denial of Service (DDoS): Attacks in which a large number of requests are sent to a web application in order to overload it and make it inaccessible.
   
   A WAF analyzes HTTP and HTTPS traffic and applies specific rules and filters to identify and block suspicious activity. It can be implemented both at server level and as a cloud-based solution and is an important part of a comprehensive security strategy for web applications.

CWE stands for "Common Weakness Enumeration." It is a standardized list of known security vulnerabilities and weaknesses commonly found in software applications and systems. Managed and maintained by the MITRE Corporation, a nonprofit organization, CWE serves as a reference for security professionals, developers, and organizations to identify, understand, and address vulnerabilities.

CWE contains several hundred entries, each with a unique number and description, categorized into various groups, including injection flaws, cross-site scripting (XSS), authentication issues, sensitive data exposure, and cryptographic weaknesses.

It serves as a valuable tool for risk assessment, security analysis, and software development, helping developers understand and mitigate security vulnerabilities before they can be exploited. CWE is often used in conjunction with other security standards and guidelines, such as the Common Vulnerability Scoring System (CVSS) and the OWASP Top Ten.

XML External Entity (XXE)-Injection is a type of attack targeting XML processing vulnerabilities in applications. In an XXE attack, an attacker attempts to introduce malicious external entities into XML documents and persuade the application to process these entities. This can lead to security issues, including theft of sensitive data, remote code execution, or denial of services.

Here's a basic explanation of how an XXE attack works:

1. An attacker manipulates an XML document being processed by the targeted application by inserting malicious external entities into the document. An external entity is a reference to an external resource typically defined in a Document Type Definition (DTD) or XML Schema.

2. The attacker attempts to coax the application into processing the malicious external entities, for example, by sending a specially crafted HTTP request or XML data to the application.

3. When the application processes the malicious external entities, it can have various effects, including accessing sensitive files or data on the server, executing remote code, or denying services.

A typical example of an XXE attack is stealing sensitive files, such as the contents of configuration files or password files on the server. Through clever manipulation of the XML document, an attacker can persuade the application to disclose the contents of these files.

To protect against XXE attacks, developers need to carefully examine how XML data is processed in their applications. They should ensure they use secure XML parsers, disable external entities, avoid using XML data directly in conjunction with confidential files or data, and thoroughly validate and filter incoming XML data to remove unwanted entities. Enabling XML schema validation and using Content Security Policies can also help prevent XXE attacks. It's also important for administrators to regularly audit their systems and applications for known XXE vulnerabilities and install security updates to minimize potential attack vectors.