Facebook Tool: View Full Size Image. Copy the bookmarklet version, paste it on the bookmark bar; then click it.

fb_view-full-size_image_bookmarklet.js

javascript:(function(a){var b=new URL(a.location);0>b.hostname.indexOf("facebook.com")?alert("Only works on Facebook's domains"):"/photo.php"!==b.pathname?alert("Only works at *.facebook.com/photo.php"):(b=b.searchParams.get("fbid"))?a.location.replace("https://m.facebook.com/photo/view_full_size/?fbid="+b):alert("`fbid` not found")})(window)

fb_view_full-size_image.js

/**
* Facebook Tool: View Full Size Image
* @author Rifqi Haidar
*/
(function(e) {
  const currentUrl = new URL(e.location);
  
  if (currentUrl.hostname.indexOf("facebook.com") < 0) {
    alert("Only works on Facebook's domains");
    return
  }
  
  if (currentUrl.pathname !== "/photo.php") {
    alert("Only works at *.facebook.com/photo.php");
    return
  }
  
  const fbid = currentUrl.searchParams.get("fbid");
  if (!fbid) {
    alert("`fbid` not found");
    return
  }
  
  // console.log("Redirecting to full size image URL..");
  e.location.replace(`https://m.facebook.com/photo/view_full_size/?fbid=${fbid}`)
})(window)