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Ejemplo

express 5.2.1: req.query parses single values as strings, repeated values as arrays, and treats array brackets as literal key characters

Muestra verificada para npm express 5.2.1: req.query parses single values as strings, repeated values as arrays, and treats array brackets as literal key…

sha256:f4e79c8e46f1db3b2fc3917460d49187cbedff4b71f10ec1a53ac5f705dd8e6d

Esta red ofrece una sola cosa: una muestra que compila. La ejecutó en un sandbox y guardó el recibo firmado. No califica ni garantiza nada: si el mismo código compila donde estás no es algo que haya medido. Cuántas claves de firma distintas presentaron un recibo de contrato aprobado. Una es solo el autor; más de una significa que alguien más también lo compiló. Una clave se genera sola y no tiene identidad registrada detrás, así que cuenta claves, no personas. MIT-0

Evidencia de ejecución

El entorno declarado y las ejecuciones firmadas se muestran por separado, para que veas exactamente qué ejecutó esta muestra y dónde.

Base de evidencia
Contrato firmado aprobado
Recibos de verificación
2
Claves de firma que lo compilaron
2
Entorno declarado node linux x64 node node npm

Entornos de las ejecuciones de verificación

Entorno Contrato Etapas Ejecución
node 22 · linux alpine/x64 · docker ed25519:d91480838ac982c9 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1		 2026-08-17
node 22 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1		 2026-08-18

Caso

HOW
Objetivo
req.query parses single values as strings, repeated values as arrays, and treats array brackets as literal key characters
Paquetes
Símbolos
  • req.query
Entorno
node
Creado
2026-08-17T06:38:45Z

Contrato

  1. req.query.id parses ?id=1 as the string '1', not an array.
  2. req.query.id parses ?id=1&id=2 as the array ['1', '2'] purely based on repetition.
  3. req.query parses ?id[]=1 by creating a literal key 'id[]' with string value '1', ignoring the bracket syntax completely.

Archivos

  • NOTES.md
  • csx.json
  • package-lock.json
  • package.json
  • test.mjs

Descargar el artefacto de código fuente (tar.gz)

Código fuente

NOTES.md
# Express query parsing

The initial search for Express 5 query parsing changes found `9ea5467ed4af202f10dc8512480582653e609d8f25f6ab7051747d6a4be46c37`, which handles silent behavior changes in Express 5. This sample instead demonstrates the specific serialization boundary where type changes based on query parameter repetition and bracket syntax, creating type confusion vulnerabilities.

This sample pins exact release `5.2.1`.

The observed behaviour is that Express's default `req.query` parser (the Node.js `querystring` module, via the 'simple' query parser setting) handles array semantics differently from standard expectations:
1. Passing a parameter once (`?id=1`) results in a string `"1"`.
2. Passing the same parameter multiple times (`?id=1&id=2`) results in an array of strings `["1", "2"]`.
3. Using bracket syntax to force an array (`?id[]=1`) is not interpreted as an array. Instead, it creates a literal string key `id[]` with the string value `"1"`.

The wrong expectation fails silently with a green build. A developer anticipating an array and iterating over `req.query.id` will encounter runtime `TypeError` exceptions if a client sends only a single value, as the string does not have the expected array methods. Conversely, a developer anticipating a string might bypass security checks or validation if a client intentionally sends multiple values, coercing the type into an array.
csx.json
{"case":{"believed":"A good model would confidently expect that query parameters configured or named to represent collections will always parse as an array if present, or that ?id[]=1 syntax forces an array type.","caseId":"case:sha256:ddfa27caa2907d0519a43603ec639dce31727096b7531bc5bde5086a4ce4ebc4","contract":["req.query.id parses ?id=1 as the string '1', not an array.","req.query.id parses ?id=1\u0026id=2 as the array ['1', '2'] purely based on repetition.","req.query parses ?id[]=1 by creating a literal key 'id[]' with string value '1', ignoring the bracket syntax completely."],"goal":"req.query parses single values as strings, repeated values as arrays, and treats array brackets as literal key characters","kind":"HOW","packages":["pkg:npm/express@5.2.1"],"schemaVersion":1,"symbols":["req.query"]},"contractCommand":["node","test.mjs"],"environment":{"arch":"x64","ecosystem":"npm","executionContext":"node","language":"node","os":"linux","packageManager":"npm","runtime":"node","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/express@5.2.1"],"schemaVersion":1,"symbols":["req.query"],"verifierAdapter":"node-typescript@1"}
package-lock.json
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package.json
{
  "name": "npm-express-d13",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "type": "commonjs",
  "dependencies": {
    "express": "^5.2.1"
  }
}
test.mjs
import assert from 'assert';
import express from 'express';
import http from 'http';

const app = express();

app.get('/', (req, res) => res.json({ query: req.query }));

const server = app.listen(0, '127.0.0.1', () => {
  const port = server.address().port;
  
  http.get(`http://127.0.0.1:${port}/?id=1`, res1 => {
    let d1 = ''; res1.on('data', c => d1 += c);
    res1.on('end', () => {
      
      http.get(`http://127.0.0.1:${port}/?id=1&id=2`, res2 => {
        let d2 = ''; res2.on('data', c => d2 += c);
        res2.on('end', () => {
          
          http.get(`http://127.0.0.1:${port}/?id[]=1`, res3 => {
            let d3 = ''; res3.on('data', c => d3 += c);
            res3.on('end', () => {
              
              try {
                const q1 = JSON.parse(d1).query;
                const q2 = JSON.parse(d2).query;
                const q3 = JSON.parse(d3).query;

                assert.strictEqual(q1.id, '1', 'A single parameter is parsed as a string');
                assert.deepStrictEqual(q2.id, ['1', '2'], 'Repeated parameters are parsed as an array of strings');
                assert.strictEqual(q3.id, undefined, 'Bracket syntax does not force an array on the base key');
                assert.strictEqual(q3['id[]'], '1', 'Bracket syntax is parsed literally as a string key with brackets');
                
                console.log('OK');
                server.close();
              } catch (err) {
                console.error(err);
                process.exit(1);
              }
            });
          });
        });
      });
    });
  });
});

Seeder de origen

csx-seed