Secure File-Upload Best Practices for Customer Support
When customers need to send documents, screenshots or identification during a support interaction, they expect a smooth experience and reassurance that their data is safe. Yet uploading files through chat widgets or web forms can open a back door to attackers. In fact, security vendor OPSWAT warns that file uploads are both essential and risky: they're core to services like content management systems, healthcare portals and messaging apps, but unrestricted uploads create a major attack vector[1].
This article looks at why secure uploads matter and how you can protect your customers in 2025. Whether you build your own form, use Intercom's native attachment feature, or rely on a third-party solution like Fibre, these best practices will help keep sensitive data safe.
Why secure file uploads matter
Protect your infrastructure. Attackers can overwrite existing files or upload malware disguised as harmless documents. OPSWAT notes that malicious files can overwrite critical files (e.g., configuration files) or exploit vulnerabilities in server-side file handling[1]. The result can be downtime, ransom demands or full server compromise.
Protect your users. Malware hidden inside uploaded files doesn't just threaten your servers – it can infect your customers' devices. Embedded macros or scripts in Office documents and PDFs are a common vector[1].
Prevent service disruption. Unrestricted file uploads allow users (or bots) to upload massive files, consuming storage and bandwidth. This can degrade performance and block legitimate customers[1].
Because attacks continue to evolve, secure file-upload practices aren't static. Below are ten proven measures you should adopt for 2025.
Ten best practices for secure file uploads
1. Limit allowed file types
Restrict uploads to file extensions and MIME types you explicitly need. Reject executable formats and scripts such as .exe, .js or .bat. OPSWAT recommends limiting the allowed list to avoid malicious content[1].
2. Verify file signatures
Don't rely solely on file extensions. Attackers can rename a malicious .exe to .docx to bypass extension checks. Verify that the file's magic bytes (file signature) match the expected format before accepting it[1].
3. Scan files for malware
Every uploaded file should be scanned using up-to-date antivirus engines. OPSWAT suggests multiscanning with multiple engines for higher detection rates[1]. In a chat integration like Intercom, scanning can occur during upload or before transferring the file to storage.
4. Strip embedded content
Office and PDF files can contain hidden scripts and macros. Use content disarm and reconstruction (CDR) to remove embedded objects before the file is released to agents[1]. CDR cleans content by rebuilding it into a safe version while preserving usability.
5. Authenticate uploaders
Require users to be authenticated before uploading sensitive documents. While this doesn't guarantee their machine isn't compromised, it prevents anonymous abuse[1]. It also helps you trace back malicious activity.
6. Set size and name limits
Set maximum file sizes and restrict file-name lengths and characters. Long names or huge files can exhaust storage and disrupt service[1]. Communicate limits clearly in your UI so users know what's allowed.
7. Randomize stored file names
Rename uploaded files on the server to a unique identifier. This prevents attackers from predicting file locations and reduces the risk of direct file access[1].
8. Store files outside the web root
Never store uploaded files in a publicly accessible directory. Place them outside your web root so they can't be executed via URL[1]. For chat-based uploads, stream files directly to a secure storage service rather than writing them to your application server.
9. Check for vulnerabilities in software/firmware files
If you accept firmware or software uploads (e.g., for device support), scan for known vulnerabilities before storing them[1]. Tools like static analysis and vulnerability scanning can automate this.
10. Avoid information-rich error messages
When rejecting files, don't expose directory paths or server configuration details. Give generic error messages so attackers can't learn about your infrastructure[1].
How Fibre implements these practices
For Intercom users, Fibre simplifies secure document collection by enforcing many of these controls out of the box. When customers click the Upload Documents button in the chat widget, Fibre opens a sheet where they can drag-and-drop files. Here's how Fibre aligns with best practices:
Files never pass through our servers
Fibre streams encrypted bytes directly to your chosen storage (S3, Google Drive, or Azure Blob Storage)[2]. Because files don't reside on Fibre's infrastructure, attackers can't exploit your chat provider to reach your servers.
Enforce allowed types and size limits
Admins can whitelist specific file types (PDF, DOC, DOCX, XLS, XLSX, PPT, PPTX, PNG, JPG, GIF) and set a maximum size up to 1 GB per file in the interface[2]. Customers see these limits before uploading, reducing frustration.
Streamlined compliance
Fibre records metadata (upload time, uploader identity, IP address) for audit trails and lets you set retention policies[2]. Because you control storage, you can apply virus scanning and CDR at your endpoint before staff open the file.
Seamless user experience
Customers don't need to leave the chat to share documents. They upload directly in Intercom, and the files appear in your cloud drive, ready for review.
Conclusion
Secure file uploads are no longer optional. As remote work and online customer support grow, attackers increasingly target chat tools and web forms. By following best practices—restricting file types, verifying signatures, scanning for malware, stripping embedded content and controlling storage—you protect both your infrastructure and your users.
Fibre implements these measures in a way that feels invisible to customers but reassuring to compliance teams. Because files stream directly to your storage and never touch Fibre's servers, you keep control over sensitive data while providing a smooth upload experience.
If you're still sharing Google Drive links or relying on native chat attachments that cap file size and store data on third-party servers, it's time to modernise. Adopt secure upload practices today and give your support team—and your customers—the peace of mind they deserve.
Ready to secure your file uploads?
Fibre helps you implement secure file upload best practices inside Intercom without storing any customer files. Get started in minutes and give your team the security controls they need.
References
- [1]OPSWAT. File Upload Protection – 10 Best Practices for Preventing Cyber Attacks. Available at: opswat.com/blog/file-upload-protection-best-practices
- [2]Fibre. Introducing Fibre: Document collection inside Intercom, without the storage headache. Available at: fibrehq.com/blog/introducing-fibre