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.

Antriksh Narang Antriksh Narang 5 years+ Experienced Dev (Specially in Web Development), can help in python, javascript, react, next.js and full stack web dev technologies. 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. Anthony Akpan Anthony Akpan Developer with 8 years of experience building softwares fro startups Rudra Bhikadiya Rudra Bhikadiya I build and fix web apps across Next.js, Node.js, and DBs. Comfortable jumping into messy code, broken APIs, and mysterious bugs. If your project works in theory but not in reality, I help close that gap. Sage Fulcher Sage Fulcher Hey I'm Sage! Im a Boston area software engineer who grew up in South Florida. Ive worked at a ton of cool places like a telehealth kidney care startup that took part in a billion dollar merger (Cricket health/Interwell health), a boutique design agency where I got to work on a ton of exciting startups including a photography education app, a collegiate Esports league and more (Philosophie), a data analytics as a service startup in Cambridge (MA) as well as at Phillips and MIT Lincoln Lab where I designed and developed novel network security visualizations and analytics. I've been writing code and furiously devoted to using computers to make people’s lives easier for about 17 years. My degree is in making computers make pretty lights and sounds. Outside of work I love hip hop, the Celtics, professional wrestling, magic the gathering, photography, drumming, and guitars (both making and playing them) rayush33 rayush33 JavaScript (React.js, React Native, Node.js) Developer with demonstrated industry experience of 4+ years, actively looking for opportunities to hone my skills as well as help small-scale business owners with solutions to technical problems 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. David Olverson David Olverson Solo dev shipping production apps with AI-assisted development. I specialize in rescuing broken Lovable/Bolt/Cursor builds and taking them to production. 10+ apps shipped including SaaS CRMs, gaming platforms, real estate tools, and Discord bots. Stack: Next.js 16, TypeScript, Tailwind CSS, FastAPI, PostgreSQL, Prisma. I use Claude Code with 50+ custom skills for rapid delivery. Average turnaround: 2-4 weeks from broken prototype to production. Mehdi Ben Haddou Mehdi Ben Haddou - Founder of Chessigma (1M+ users) & many small projects - ex Founding Engineer @Uplane (YC F25) - ex Software Engineer @Amazon and @Booking.com Dor Yaloz Dor Yaloz SW engineer with 6+ years of experience, I worked with React/Node/Python did projects with React+Capacitor.js for ios Supabase expert

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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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