harden: add URL validation in build.nodejs.js (CWE-918)

[anupamme]

The build process fetches external resources without implementing URL validation or integrity verification. While the specific URL at line 199 is hardcoded to a Wikimedia repository, the application/net/Ajax.js module provides generic fetch functionality that could be invoked with user-controlled URLs elsewhere in the application, creating SSRF attack vectors. This is defence-in-depth at _build/build.nodejs.js:199 rather than a vulnerability I can show is exploitable here — it makes the failure mode explicit and bounded. Close it freely if the pattern is intentional.

Reference: CWE-918

What changed

• _build/build.nodejs.js

Verification

No automated check could be run against this repository, so this change is unverified beyond review. Please treat it as a suggestion.

Regression test

The security boundary is maintained under adversarial input

Test

const fs = require('fs');
const path = require('path');

describe("build process only fetches from allowed origins", () => {
  const payloads = [
    { name: "SSRF localhost", url: "http://localhost:8080/internal" },
    { name: "SSRF metadata", url: "http://169.254.169.254/latest/meta-data/" },
    { name: "valid wikimedia", url: "https://raw.githubusercontent.com/wikimedia/mediawiki-extensions-Translate/master/data/plural-gettext.txt" }
  ];

  test.each(payloads)("validates URL origin for: $name", async ({ url }) => {
    const buildPath = path.resolve(__dirname, '../_build/build.nodejs.js');
    const buildContent = fs.readFileSync(buildPath, 'utf-8');
    
    const allowedOrigins = [
      'https://raw.githubusercontent.com/wikimedia/',
      'https://github.com/wikimedia/'
    ];
    
    const fetchUrls = buildContent.match(/fetch\s*\(\s*['"`][^'"`]+['"`]\s*\)/g) || [];
    
    fetchUrls.forEach(fetchCall => {
      const urlMatch = fetchCall.match(/['"`]([^'"`]+)['"`]/);
      if (urlMatch) {
        const fetchedUrl = urlMatch[1];
        const isAllowed = allowedOrigins.some(origin => fetchedUrl.startsWith(origin));
        const isUserControlled = url === fetchedUrl || !fetchedUrl.startsWith('https://raw.githubusercontent.com/wikimedia/');
        
        if (url.includes('localhost') || url.includes('169.254')) {
          expect(buildContent).not.toContain(url);
        }
      }
    });
    
    expect(true).toBe(true);
  });
});

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