Overview
Some websites claim that preventing users from pasting passwords somehow improves security. In Let Them Paste Passwords, the National Cyber Security Centre says that this claim is unfounded.
Password pasting improves security because it enables users to use password managers. Password managers typically generate strong passwords for users, store them securely, and then automatically paste them into password fields whenever users need to log in.
See The "Cobra Effect" That Is Disabling Paste On Password Fields for more on why enabling pasting is a better security practice.
Recommendations
Remove the code that's preventing users from pasting into password fields. It's probably a call
to preventDefault() within the paste event listener that's associated to the password
input element.
let input = document.querySelector('input');
input.addEventListener('paste', (e) => {
e.preventDefault(); // This is what prevents pasting.
});
Find and inspect the code that's preventing pasting
To quickly find and inspect the code that's preventing pasting, try enabling the Clipboard >
paste checkbox in the Event Listener Breakpoints section of Chrome DevTools, then
pasting into a password field. DevTools should pause on the first line of code in the paste
event listener.
More information
Lighthouse gathers all <input type="password"> elements, pastes some text into each element,
and then verifies that the element's content has been set to the pasted text. If a page
doesn't use <input type="password"> for its password input fields, Lighthouse doesn't detect
those elements. It's also possible to prevent pasting outside of a paste event listener.
Lighthouse doesn't detect that scenario, either.