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.
const page = pageArea[$toHTML]().html;
      mainHtml.children.push(page);
      if (leader) {
        this[$extra].noLayoutFailure = true;
        page.children.push(leader[$toHTML](pageArea[$extra].space).html);
        leader = null;
      }
      if (trailer) {
        this[$extra].noLayoutFailure = true;
        page.children.push(trailer[$toHTML](pageArea[$extra].space).html);
        trailer = null;
      }
      const contentAreas = pageArea.contentArea.children;
      const htmlContentAreas = page.children.filter(node =>
        node.attributes.class.includes("xfaContentarea")
      );
      hasSomething = false;
      this[$extra].firstUnsplittable = null;
      this[$extra].noLayoutFailure = false;
      const flush = index => {
        const html = root[$flushHTML]();
        if (html) {
          hasSomething =
            hasSomething || (html.children && html.children.length !== 0);
          htmlContentAreas[index].children.push(html);
        }
      };
      for (let i = startIndex, ii = contentAreas.length; i < ii; i++) {
        const contentArea = (this[$extra].currentContentArea = contentAreas[i]);
        const space = { width: contentArea.w, height: contentArea.h };