[{"data":1,"prerenderedAt":205},["ShallowReactive",2],{"blog-checklists/file-upload-checklist":3},{"id":4,"title":5,"body":6,"category":182,"date":183,"dateModified":183,"description":184,"draft":185,"extension":186,"faq":187,"featured":185,"headerVariant":190,"image":191,"keywords":191,"meta":192,"navigation":193,"ogDescription":194,"ogTitle":191,"path":195,"readTime":191,"schemaOrg":196,"schemaType":197,"seo":198,"sitemap":199,"stem":200,"tags":201,"twitterCard":203,"__hash__":204},"blog/blog/checklists/file-upload-checklist.md","File Upload Security Checklist: 14-Item Guide for Safe Uploads",{"type":7,"value":8,"toc":176},"minimark",[9,16,19,22,47,65,83,98,112,117,120,123,145,164],[10,11,12],"tldr",{},[13,14,15],"p",{},"File uploads are dangerous. Validate file types by content (not extension), set size limits, store files outside your web root, generate random filenames, and never execute uploaded content. 5 critical items must be fixed before launch, 5 important items within the first week, and 4 recommended items when you can.",[13,17,18],{},"File uploads are one of the most dangerous features you can add to an app. Every uploaded file is essentially untrusted input until proven otherwise, and a single oversight can let attackers execute code on your server. If you are accepting uploads from users, do not skip any of these.",[20,21],"print-button",{},[23,24,26,31,35,39,43],"checklist-section",{"title":25},"Quick Checklist (5 Critical Items)",[27,28],"checklist-item",{"description":29,"label":30},"Check magic bytes or MIME type, never trust extensions alone","Validate file type by content",[27,32],{"description":33,"label":34},"Only accept specific file types you need, reject everything else","Whitelist allowed file types",[27,36],{"description":37,"label":38},"Uploaded files should never be directly accessible via URL","Store outside web root",[27,40],{"description":41,"label":42},"Treat all uploads as untrusted data","Never execute uploaded content",[27,44],{"description":45,"label":46},"Verify users can only access their own uploads","Implement authorization checks",[23,48,51,54,57,61],{"title":49,"count":50},"File Validation","4",[27,52],{"description":53,"label":30},"Check magic bytes or use MIME detection libraries. Never trust file extensions alone. How to validate file types",[27,55],{"description":56,"label":34},"Only accept specific file types you need. Reject everything else. Never blacklist. How to whitelist file types",[27,58],{"description":59,"label":60},"Prevent denial of service from large uploads. Set limits at both client and server. How to limit upload sizes","Set maximum file size limits",[27,62],{"description":63,"label":64},"Remove special characters, path traversal sequences (../), and null bytes from filenames. How to sanitize filenames","Sanitize filenames",[23,66,68,71,75,79],{"title":67,"count":50},"Storage Security",[27,69],{"description":70,"label":38},"Uploaded files should never be directly accessible via URL in your application directory. How to secure file storage",[27,72],{"description":73,"label":74},"S3, Cloud Storage, or similar. Serve files via time-limited signed URLs for access control. How to use signed URLs","Use cloud storage with signed URLs",[27,76],{"description":77,"label":78},"Do not use original filenames. Generate UUIDs or random strings to prevent conflicts and enumeration. How to generate secure filenames","Generate random filenames",[27,80],{"description":81,"label":82},"Serve files with Content-Type header matching actual type. Add Content-Disposition: attachment for downloads. How to set content headers","Set correct content types when serving",[23,84,87,91,95],{"title":85,"count":86},"Malware Protection","3",[27,88],{"description":89,"label":90},"Use ClamAV or cloud-based scanning for documents and executables. Block detected threats. How to scan for malware","Scan uploads for malware",[27,92],{"description":93,"label":94},"Process and re-encode uploaded images. This strips embedded scripts and metadata. How to re-encode images","Re-encode images",[27,96],{"description":97,"label":42},"Uploaded files should never be interpreted or executed. Treat all uploads as untrusted data. How to prevent execution",[23,99,101,104,108],{"title":100,"count":86},"Access Control",[27,102],{"description":103,"label":46},"Verify users can only access their own uploads. Check permissions on every download request. How to authorize file access",[27,105],{"description":106,"label":107},"Prevent abuse by limiting how many files and how much data users can upload. How to rate limit uploads","Rate limit upload requests",[27,109],{"description":110,"label":111},"Track who uploads what. Useful for abuse detection and incident investigation. How to log upload activity","Log upload activity",[113,114,116],"h2",{"id":115},"uploads-are-a-major-attack-vector","Uploads Are a Major Attack Vector",[13,118,119],{},"File uploads are consistently one of the most dangerous features to implement. A single vulnerability can let attackers upload malicious scripts and gain full control of your server. The OWASP top 10 includes unrestricted file uploads as a critical risk.",[13,121,122],{},"When in doubt, do not accept uploads at all. If you must, use cloud storage with signed URLs, validate everything, and never execute uploaded content.",[124,125,126,133,139],"faq-section",{},[127,128,130],"faq-item",{"question":129},"How do I validate file types securely?",[13,131,132],{},"Do not trust file extensions. Check the file content using magic bytes or MIME type detection libraries. Even then, be cautious. Attackers can craft files that pass MIME checks but contain malicious content.",[127,134,136],{"question":135},"Should I scan uploaded files for malware?",[13,137,138],{},"Yes, if accepting files that could contain malware (documents, executables). Use services like ClamAV or cloud-based scanning APIs. For images, re-encoding can strip embedded malware.",[127,140,142],{"question":141},"Is it safe to accept image uploads?",[13,143,144],{},"Images are safer than documents or executables but still risky. Validate MIME type, re-encode using an image library (strips metadata and embedded code), and serve from a separate domain or cloud storage.",[146,147,148,154,159],"related-articles",{},[149,150],"related-card",{"description":151,"href":152,"title":153},"Secure your API endpoints","/blog/checklists/api-security-checklist","API Security Checklist",[149,155],{"description":156,"href":157,"title":158},"Step-by-step implementation guide","/blog/how-to/secure-file-uploads","How to Implement Secure File Uploads",[149,160],{"description":161,"href":162,"title":163},"Secure file delivery with S3","/blog/how-to/use-signed-urls","How to Use S3 Signed URLs",[165,166,169,173],"cta-box",{"href":167,"label":168},"/","Start Free Scan",[113,170,172],{"id":171},"check-your-upload-security","Check Your Upload Security",[13,174,175],{},"Scan your application for file upload vulnerabilities.",{"title":177,"searchDepth":178,"depth":178,"links":179},"",2,[180,181],{"id":115,"depth":178,"text":116},{"id":171,"depth":178,"text":172},"checklists","2026-01-29","Security checklist for file uploads. Validate file types, scan for malware, secure storage, and prevent common file upload vulnerabilities in your application.",false,"md",[188,189],{"question":129,"answer":132},{"question":135,"answer":138},"green",null,{},true,"Security checklist for file uploads covering validation and storage security.","/blog/checklists/file-upload-checklist","[object Object]","HowTo",{"title":5,"description":184},{"loc":195},"blog/checklists/file-upload-checklist",[202],"Security Checklist","summary_large_image","8SieQEIeERCaGuY82Lv6BfELzUeP3ZjpvlFdCNVoR8U",1775843931039]