Replit ui

XSS Vulnerability in Thymeleaf Templates

XSS attacks are possible through template injection. Attacker-controlled input executes JavaScript on victim's browser.

Improper escaping of user input in templates allows script execution.

Common Causes

  1. Using th:utext instead of th:text (unescaped)
  2. Raw HTML from database without sanitization
  3. User input directly in JavaScript context
  4. th:onclick, th:onhover with user data

How to Fix It

Always use th:text (escapes HTML). Use th:utext only for trusted content. Never put user input in script blocks or event handlers. Sanitize HTML with OWASP Java HTML Sanitizer. Use CSP (Content Security Policy) header. Test with OWASP ZAP.

Real developers can help you.

Yovel Cohen Yovel Cohen I got a lot of experience in building Long-horizon AI Agents in production, Backend apps that scale to millions of users and frontend knowledge as well. Daniel Vázquez Daniel Vázquez Software Engineer with over 10 years of experience on Startups, Government, big tech industry & consulting. Jacek Rozanski Jacek Rozanski Senior PHP/Symfony developer and DevOps engineer with 20+ years of professional experience, running opcode.pl (web development agency, est. 2004). Day job: I'm the sole backend developer at merketing company where I own and maintain 11 PHP/Symfony microservices on AWS (ECS Fargate, RDS, S3, CloudFront), handle the full CI/CD pipeline (Bitbucket Pipelines, Docker), and manage monitoring with Sentry and CloudWatch. These services handle high request volumes in production every month. What I bring to AI-built apps: - I audit and fix security issues (OWASP methodology), performance bottlenecks, and architectural problems in codebases generated by Cursor, Claude Code, Lovable, Bolt, and v0 - I refactor AI-generated prototypes into production-grade applications with proper error handling, testing, and clean architecture (SOLID, DDD, hexagonal architecture) - I set up the infrastructure AI tools don't touch: AWS hosting, CI/CD pipelines, automated deployments, database optimization, monitoring, and alerting - I integrate external services: payment providers, email systems, partner APIs, SSO/auth Tech stack: PHP 8.x, Symfony, React, Next.js, PostgreSQL, MySQL, Docker, AWS (ECS, RDS, S3, SQS/SNS, CloudFront), Terraform, Supabase. I also use AI tools daily (Claude Code, Cursor) in my own workflow, so I understand both the strengths and the gaps in AI-generated code. Based in Poland (CET timezone). Available for async work and calls during EU/US business hours. Nam Tran Nam Tran 10 years as fullstack developer MFox MFox Full-stack professional senior engineer (15+years). Extensive experience in software development, qa, and IP networking. Pratik Pratik SWE with 15+ years of experience building and maintaining web apps and extensive BE infrastructure Basel Issmail Basel Issmail ’m a Senior Full-Stack Developer and Tech Lead with experience designing and building scalable web platforms. I work across the full development lifecycle, from translating business requirements into technical architecture to delivering reliable production systems. My work focuses on modern web technologies, including TypeScript, Angular, Node.js, and cloud-based architectures. I enjoy solving complex technical problems and helping teams turn product ideas and prototypes into working platforms that can grow and scale. In addition to development, I often collaborate closely with product managers, business analysts, designers, and QA teams to ensure that solutions align with both technical and business goals. I enjoy working with startups and product teams where I can contribute both as a hands-on engineer and as a technical partner in designing and delivering impactful software. Jared Hasson Jared Hasson Full time lead founding dev at a cyber security saas startup, with 10 yoe and a bachelor's in CS. Building & debugging software products is what I've spent my time on for forever Richard McSorley Richard McSorley Full-Stack Software Engineer with 8+ years building high-performance applications for enterprise clients. Shipped production systems at Walmart (4,000+ stores), Cigna (20M+ users), and Arkansas Blue Cross. 5 patents in retail/supply chain tech. Currently focused on AI integrations, automation tools, and TypeScript-first architectures. Kingsley Omage Kingsley Omage Fullstack software engineer passionate about AI Agents, blockchain, LLMs.

You don't need to be technical. Just describe what's wrong and a verified developer will handle the rest.

Get Help

Frequently Asked Questions

What's the difference between th:text and th:utext?

th:text escapes HTML (safe), th:utext outputs raw HTML (unsafe for user input)

How do I sanitize user-provided HTML?

Use OWASP Java HTML Sanitizer library with whitelist approach

Related Replit Issues

Can't fix it yourself?
Real developers can help.

You don't need to be technical. Just describe what's wrong and a verified developer will handle the rest.

Get Help