[BE-91] File upload validation and malware scanning (clamscan is installed but unused)

[yusuftomilola]

Overview

clamscan is in backend/package.json dependencies but imported nowhere (grep -rl clamscan backend/src → 0 files). Uploads flow through multer/cloudinary with no verified size, type, or content checks. Either wire it up or drop the dependency.

Tasks

• Add a reusable upload validation pipe: max size per type, MIME allowlist, and magic-byte sniffing (do not trust the client-supplied Content-Type or file extension).
• Wire clamscan into the upload path — reject infected files with 422 and log the detection; make the scanner optional via env flag so local dev without a ClamAV daemon still works.
• Strip EXIF metadata from images with the already-installed sharp (removes GPS location from member photos).
• Enforce limits centrally so every upload route inherits them.
• If maintainers prefer not to run ClamAV, remove clamscan from dependencies instead.

Acceptance Criteria

• Uploading a .exe renamed to .jpg is rejected by magic-byte checking.
• Oversized uploads are rejected before hitting Cloudinary.
• EXIF GPS data is absent from stored images.
• clamscan is either used or removed — no dead dependency remains.

Notes for Contributors

Comment below to be assigned.

[Michealshodipo56]

@Michealshodipo56 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I would like to work on this kindly assign me

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[khanavi272-spec]

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I would like to work on this issue

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[S-Mubarak]

@S-Mubarak has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello, I'm interested in taking this issue on.

I'm a software engineer with strong experience in JavaScript and building scalable web applications. I'm comfortable working across the stack, writing clean, maintainable code, and collaborating in open source environments.

I've looked into this issue closely and I'm confident in my ability to deliver a high-quality implementation here.

Looking forward to contributing — please assign this issue to me.

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Congratulations, @S-Mubarak! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@S-Mubarak's PR #1566 was approved and merged by @yusuftomilola.

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👏 Great work, @S-Mubarak! Keep contributing to DistinctCodes.

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