fix(files): escape user filenames in the Content-Disposition header

[waleedlatif1]

Summary

• escape the user-supplied filename before it is interpolated into the quoted filename parameter, so it cannot terminate the parameter or append parameters of its own
• always percent-encode the filename* ext-value fully, including the characters encodeURIComponent leaves raw
• filenames that are already safe printable ASCII keep their exact previous header, so ordinary downloads are unchanged
• a control character in a name no longer produces an invalid header value (that previously made the download 500)

Type of Change

• Bug fix

Testing

Added unit tests covering each case, including that an ordinary filename is byte-identical to before. app/api/files suite passes (247 tests); type-check and lint clean.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

[vercel]

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Aug 8, 2026 7:30pm

[cursor]

PR Summary

Medium Risk
Touches security-sensitive download response headers driven by user-supplied names; the change is localized to filename encoding with thorough tests, limiting blast radius.

Overview
Hardens encodeFilenameForHeader so attacker-controlled download names cannot break or inject Content-Disposition parameters when files are served.

The quoted filename value is now built from sanitized ASCII (stripping ", \\, ;, and non-printable characters), and unsafe names also emit a single filename* ext-value via encodeExtValue, which percent-encodes characters encodeURIComponent leaves raw (notably ' in the UTF-8'' delimiter). Safe printable ASCII names still get the same filename="..." header as before.

Control characters in a name no longer produce invalid header values that could fail the response. Unit tests cover injection via quotes/filename*, apostrophes, CRLF, and ordinary filenames.

^{Reviewed by Cursor Bugbot for commit bbeee90. Configure here.}

[greptile-apps]

Greptile Summary

The PR hardens file-download Content-Disposition construction against parameter injection and invalid header characters while preserving existing output for safe ASCII filenames.

• Sanitizes the quoted filename fallback.
• Fully percent-encodes RFC 8187 filename* values.
• Adds regression coverage for injection payloads, control characters, Unicode, apostrophes, unchanged safe names, and storage-key prefixes.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The revised encoding safely neutralizes quoted-parameter injection, emits valid percent-encoded extended values, and preserves the previous header for ordinary safe filenames.

Important Files Changed

Filename	Overview
apps/sim/app/api/files/utils.ts	Safely constructs quoted and extended filename parameters without exposing a concrete regression.
apps/sim/app/api/files/utils.test.ts	Adds focused regression tests covering unsafe, Unicode, control-character, and ordinary filename behavior.

_{Reviews (1): Last reviewed commit: "fix(files): escape user filenames in the..." | Re-trigger Greptile}