Courses
1. Introduction to Blockchain and Solana
2. Setting Up Your Development Environment
3. Solana Architecture and Key Concepts
4. Creating and Managing Wallets
5. Understanding Solana Programs
6. Building Your First Solana Program
7. Deploying Programs on the Solana Network
8. Interacting with Solana Programs
9. Using Solana CLI and SDKs
10. Developing Decentralized Applications (DApps)
11. Smart Contract Security Best Practices
12. Testing and Debugging Solana Programs
13. Optimizing Performance on Solana
14. Exploring Solana Ecosystem Tools
1. Introduction to Blockchain and Ethereum
2. Setting Up Your Development Environment
3. Ethereum Architecture and Key Concepts
4. Creating and Managing Wallets
5. Understanding Smart Contracts
6. Building Your First Smart Contract
7. Deploying Smart Contracts on the Ethereum Network
8. Interacting with Smart Contracts
9. Using Ethereum CLI and SDKs
10. Developing Decentralized Applications (DApps)
11. Smart Contract Security Best Practices
12. Testing and Debugging Smart Contracts
13. Optimizing Performance on Ethereum
14. Exploring Ethereum Ecosystem Tools
1. Introduction to Blockchain and Polygon
2. Setting Up Your Development Environment
3. Polygon Architecture and Key Concepts
4. Creating and Managing Wallets
5. Understanding Smart Contracts on Polygon
6. Building Your First Smart Contract on Polygon
7. Deploying Smart Contracts on the Polygon Network
8. Interacting with Smart Contracts on Polygon
9. Using Polygon CLI and SDKs
10. Developing Decentralized Applications (DApps) on Polygon
11. Smart Contract Security Best Practices for Polygon
12. Testing and Debugging Smart Contracts on Polygon
13. Optimizing Performance on Polygon
14. Exploring Polygon Ecosystem Tools
1. Introduction to Cybersecurity
2. Report Writing for Penetration Testers
3. Information Gathering
4. Vulnerability Scanning
5. Introduction to Web Applications
6. Common Web Application Attacks
7. SQL Injection Attacks
8. Client-Side Attacks
9. Locating Public Exploits
10. Fixing Exploits
11. Antivirus Evasion
12. Password Attacks
13. Windows Privilege Escalation
14. Linux Privilege Escalation
15. Advanced Tunneling
16. The Metasploit Framework
17. Active Directory: Introduction and Enumeration
18. Attacking Active Directory Authentication
19. Lateral Movement in Active Directory
XML External Entity Injection
OSWE · Chapter 22
XML External Entity Injection
XML External Entity (XXE) injection abuses XML parsers that resolve external entity references by default, letting an attacker read local files, perform SSRF, or cause denial of service — entirely from a maliciously crafted XML document.
Key concepts
- The classic PoC declares an external entity pointing at a local file (`file:///etc/passwd`) and references it inside the XML body so the parser inlines the file contents into the parsed result.
- XXE can also be used for SSRF by declaring an entity pointing at an internal-only HTTP URL instead of a local file.
- The single most effective fix is disabling DTD processing and external entity resolution entirely at the parser level — most modern XML libraries default to safe behavior, but many still ship unsafe-by-default in older configurations.
- XXE is frequently reachable through unexpected surfaces: SOAP APIs, file uploads (DOCX/XLSX are ZIP archives of XML), and even SVG image uploads.
Example
<?xml version="1.0"?>
<!DOCTYPE data [<!ENTITY xxe SYSTEM "file:///etc/passwd">]>
<data>&xxe;</data>Try it yourself
On a lab XXE challenge, submit the classic file-read payload above against an endpoint that parses XML, and confirm whether the response reflects the target file's contents.