The following code is flagged as dead (since it's *replacing* rather than updating the existing Object):
https://github.com/mozilla/pdf.js/blob/4483cba72410027acf46630ebf252ae529704476/src/core/xfa/template.js#L2336-L2339
according to the alert in https://github.com/mozilla/pdf.js/security/code-scanning/103?query=ref%3Arefs%2Fheads%2Fmaster

Looking at the surrounding code, I can see a couple of possibilities here:
 1. This is indeed just dead code, which should be removed.
 2. The code should be moved up, and placed just *above* the previous block instead.
 3. There should be other, more invasive, changes made to this code...

/cc @calixteman Which solution is correct here?
Assuming it's either option 1 or 2, I can submit a patch to fix this.
pageArea = pageAreas[0];
    }
    pageArea[$extra] = {
      numberOfUse: 1,
    };
    const pageAreaParent = pageArea[$getParent]();
    pageAreaParent[$extra] = {
      numberOfUse: 1,
      pageIndex: pageAreaParent.pageArea.children.indexOf(pageArea),
      pageSetIndex: 0,
    };
    let targetPageArea;
    let leader = null;
    let trailer = null;
    let hasSomething = true;
    let hasSomethingCounter = 0;
    let startIndex = 0;
    while (true) {
      if (!hasSomething) {
        mainHtml.children.pop();
        
        if (++hasSomethingCounter === MAX_EMPTY_PAGES) {
          warn("XFA - Something goes wrong: please file a bug.");
          return mainHtml;
        }
      } else {
        hasSomethingCounter = 0;
      }
      targetPageArea = null;
      this[$extra].currentPageArea = pageArea;