return res.redirect('back'); returns to '/' instead of the previous page about express HOT 2 CLOSED

Do you receive the Referrer header? If you set Referrer-Policy: no-referrer then the browser won't send the Referrer header, which is required for res.redirect("back") to work.

from express.

@krzysdz Thank you so much. I thought back to what could be blocking the referrer and realized it was the helmet NPM package. I'll post the solution here for anyone else that runs into this issue.
From:
app.use(helmet());
To:

app.use(
  helmet({
    referrerPolicy: false,
  }),
);

from express.