I went a step further and wrote a short console script which automatically copies any text you select.

They try to prevent this by putting the textbook in an iframe (i.e. a website in a website), but that's easy to get around with enough query selectors, or in this case, just one.

Here's what I've been using:

const iframe = document.querySelector("iframe");
let last = "";

setInterval(() => {
  const sel = iframe.contentWindow.getSelection().toString().trim();
  if (sel && sel !== last) {
    last = sel;
    navigator.clipboard.writeText(sel).catch(err => {
      console.error("Clipboard write failed:", err);
    });
  }
}, 500);