Don't fuck with paste

allow_paste.js

// Open up the console and paste this in to prevent sites 
// from blocking your pastes into password fields
// This allows you to continue using your password manager
// without it being a giant PITA.
var allowPaste = function(e){
  e.stopImmediatePropagation();
  return true;
};
document.addEventListener('paste', allowPaste, true);