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Missing output encoding in `delete_json_doc`: `id` is echoed raw in the confirmation message

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
70/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
typescript
Domain
database, security

Research direction

The relevant code is the delete_json_doc case in src/index.ts, around lines 120-132. Read how id is taken from request.params.arguments and why the !id guard fails after String(...). Then check the load_json_doc and query_json_docs cases, which the issue says follow the same pattern. Done means a missing or malformed id is rejected before db.del, and the confirmation text encodes the ID instead of echoing it raw.

Written by the indexing model from the issue text.

Description

Tool: delete_json_doc · Tested commit: 605dbb7
Weakness: CWE-79 Cross-site Scripting / unescaped output

Summary

delete_json_doc deletes a document from the Fireproof json_docs database and replies Deleted document with ID: <id>, with the caller's id inserted verbatim. The ID is not validated or escaped, so markup or control characters in it come back unchanged. This only matters if a client renders tool output as HTML or Markdown, but the fix is small.

Details

src/index.ts:120-132:

case "delete_json_doc": {
  const id = String(request.params.arguments?.id);
  if (!id) {
    throw new Error("ID is required");
  }

  await db.del(id);
  return {
    content: [{
      type: "text",
      text: `Deleted document with ID: ${id}`
    }]
  };
}

There is no check on the ID's format and no encoding of the echoed value. Two related details: String(undefined) is the string "undefined", so the !id guard never fires when id is missing; and the reply says "Deleted" whether or not a document with that ID existed.

Impact

The id argument is chosen by the model and can be steered by prompt injection, and the echoed text goes back to the client. In clients that show tool results as plain text nothing happens. A client or UI that renders tool output as HTML or Markdown without escaping would render the caller's markup. Severity is low; this is a hardening issue in a demo server.

Suggested fix

Validate the ID before use (for example typeof id === "string" && /^[A-Za-z0-9_-]{1,128}$/.test(id), matching the IDs Fireproof generates), fix the missing-argument check by testing the raw argument before String(...), and return the ID JSON-encoded, for example Deleted document with ID: ${JSON.stringify(id)}. The same pattern applies to load_json_doc and query_json_docs.

Dominant language
JavaScript
Stars
31
Forks
10
No merged PRs in 30d

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First steps

  1. Read the whole issue, then the project's contributing guide.
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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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