URLVersionControlSystem/snapshot.content.js at main · premkumar127001/URLVersionControlSystem · GitHub

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// snapshot.content.js
// Returns a sanitized HTML snapshot when asked.
// - strips <script>, on* event handlers, javascript: URLs, and meta refresh.

function sanitizeDocument() {
  const root = document.documentElement.cloneNode(true);

  // Remove scripts
  root.querySelectorAll('script').forEach(s => s.remove());

  // Remove meta refresh
  root.querySelectorAll('meta[http-equiv]').forEach(m => {
    const v = (m.getAttribute('http-equiv') || '').toLowerCase();
    if (v === 'refresh') m.remove();
  });

  // Remove event handlers + dangerous URLs
  const walker = document.createTreeWalker(root, NodeFilter.SHOW_ELEMENT);
  const toFix = [];
  while (walker.nextNode()) toFix.push(walker.currentNode);
  for (const el of toFix) {
    // remove on* attributes
    [...el.attributes].forEach(attr => {
      const n = attr.name.toLowerCase();
      if (n.startsWith('on')) el.removeAttribute(attr.name);
      if (n === 'href' || n === 'xlink:href') {
        const val = (attr.value || '').trim().toLowerCase();
        if (val.startsWith('javascript:')) el.setAttribute(attr.name, '#');
      }
    });
  }

  // Prefer readable charset meta
  let html = '<!doctype html>\n' + root.outerHTML;
  return html;
}

chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
  if (msg?.type === 'uvcs.snapshot.request') {
    try {
      const html = sanitizeDocument();
      sendResponse(html);
    } catch (e) {
      sendResponse('');
    }
    return true;
  }
});