Lovable security

Insecure File Upload in Lovable App

Your Lovable app's file upload feature accepts any file type without validation, potentially allowing users to upload malicious scripts, executable files, or oversized files that could compromise your server or other users.

Without proper file validation, an attacker could upload a PHP script, an HTML file containing JavaScript, or a file disguised as an image that actually contains malware. If these files are served back to users, the malicious code could execute.

This is especially dangerous if uploaded files are stored in a publicly accessible location and served directly to users without content-type validation.

Error Messages You Might See

File type not allowed 413 Payload Too Large Storage quota exceeded Failed to upload file: permission denied
File type not allowed413 Payload Too LargeStorage quota exceededFailed to upload file: permission denied

Common Causes

  • No file type validation — The upload endpoint accepts any file regardless of extension or MIME type
  • Client-side only validation — File type checks only happen in the browser, which can be easily bypassed
  • No file size limits — Users can upload extremely large files, causing storage and bandwidth issues
  • Files served with wrong content-type — Uploaded files are served back without proper Content-Type headers, allowing browser execution
  • No malware scanning — Uploaded files are stored and served without any security scanning

How to Fix It

  1. Validate file types on the server — Check both file extension and MIME type on the backend, not just in the browser
  2. Set file size limits — Configure maximum upload sizes (e.g., 5MB for images, 25MB for documents)
  3. Rename uploaded files — Generate random filenames to prevent path traversal attacks
  4. Serve files with correct headers — Set Content-Type and Content-Disposition headers to prevent browser execution
  5. Use Supabase Storage policies — Configure bucket policies to restrict file types and sizes at the storage level

Real developers can help you.

Meïr Ankri Meïr Ankri Full-stack developer specializing in React / Next.js / Node.js with 6+ years of experience. I've worked across various sectors including automotive (Reezocar/Société Générale), healthcare (Medical Link SaaS), and e-commerce (Glasman). I build web apps end-to-end, from architecture to production, with a focus on scalability, performance, and code quality. I also mentor junior developers and contribute to technical decisions and code reviews. AUXLE AUXLE I am a Full Stack Developer experienced in building Websites, Web apps and Cross Platform Mobile Apps for Startups and Companies. Luca Liberati Luca Liberati I work on monoliths and microservices, backends and frontends, manage K8s clusters and love to design apps architecture Milan Surelia Milan Surelia Milan Surelia is a Mobile App Developer with 5+ years of experience crafting scalable, cross-platform apps at 7Span and Meticha. At 7Span, he engineers feature-rich Flutter apps with smooth performance and modern UI. As the Co-Founder of Meticha, he builds open-source tools and developer-focused products that solve real-world problems. Expertise: 💡 Developing cross-platform apps using Flutter, Dart, and Jetpack Compose for Android, iOS, and Web. 🖋️ Sharing insights through technical writing, blogging, and open-source contributions. 🤝 Collaborating closely with designers, PMs, and developers to build seamless mobile experiences. Notable Achievements: 🎯 Revamped the Vepaar app into Vepaar Store & CRM with a 2x performance boost and smoother UX. 🚀 Launched Compose101 — a Jetpack Compose starter kit to speed up Android development. 🌟 Open source contributions on Github & StackOverflow for Flutter & Dart 🎖️ Worked on improving app performance and user experience with smart solutions. Milan is always happy to connect, work on new ideas, and explore the latest in technology. Tejas Chokhawala Tejas Chokhawala Full-stack engineer with 5 years experience building production web apps using React, Next.js and TypeScript. Focused on performance, clean architecture and shipping fast. Experienced with Supabase/Postgres backends, Stripe billing, and building AI-assisted developer tools. hanson1014 hanson1014 Full-stack developer experienced in fixing and deploying AI-generated apps from Lovable, Bolt.new, Cursor, and Replit. I specialize in debugging Supabase integration issues (auth flows, RLS policies, database connections), fixing broken deployments, resolving routing/blank screen problems, and cleaning up messy React/Vite codebases. I also build production apps with the Claude API and have shipped a Mac desktop dev tool (Nexterm from scratch. Based in Hong Kong, fast turnaround. BurnHavoc BurnHavoc Been around fixing other peoples code for 20 years. 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. zipking zipking I am a technologist and product builder dedicated to creating high-impact solutions at the intersection of AI and specialized markets. Currently, I am focused on PropScan (EstateGuard), an AI-driven SaaS platform tailored for the Japanese real estate industry, and exploring the potential of Archify. As an INFJ-T, I approach development with a "systems-thinking" mindset—balancing technical precision with a deep understanding of user needs. I particularly enjoy the challenge of architecting Vertical AI SaaS and optimizing Small Language Models (SLMs) to solve specific, real-world business problems. Whether I'm in a CTO-level leadership role or hands-on with the code, I thrive on building tools that turn complex data into actionable value. Pratik Pratik SWE with 15+ years of experience building and maintaining web apps and extensive BE infrastructure

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Frequently Asked Questions

What file types should I allow?

Only allow the specific types your app needs. For profile pictures, allow only .jpg, .png, .webp. For documents, allow .pdf, .doc, .docx. Never allow .html, .js, .php, .exe, or .svg files from untrusted users.

Is Supabase Storage secure by default?

Supabase Storage requires you to set up bucket policies. By default, buckets are private, but you need to configure what file types and sizes are allowed, and who can upload.

Related Lovable Issues

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