Encrypt::hashNeedsUpdate() 

\nn\t3::Encrypt()->hashNeedsUpdate($passwordHash = '', $loginType = 'FE'); 

Checks whether the hash needs to be updated because it does not correspond to the current encryption algorithm. When updating Typo3 to a new LTS, the hashing algorithm of the passwords in the database is also often is improved. This method checks whether the transferred hash is still up-to-date or needs to be updated.

Returns true if an update is required.

\nn\t3::Encrypt()->hashNeedsUpdate('$P$CIz84Y3r6.0HX3saRwYg0ff5M0a4X1.'); // true

An automatic update of the password could look like this in a manual FE user authentication service:

$uid = $user['uid']; // uid of the FE user
$authResult = \nn\t3::Encrypt()->checkPassword( $passwordHashInDatabase, $clearTextPassword );
if ($authResult & \nn\t3::Encrypt()->hashNeedsUpdate( $passwordHashInDatabase )) {
    \nn\t3::FrontendUserAuthentication()->setPassword( $uid, $clearTextPassword );
}

| @return boolean

public function hashNeedsUpdate( $passwordHash = '', $loginType = 'FE' ) {
	// Könnte z.B. `TYPO3\CMS\Core\Crypto\PasswordHashing\PhpassPasswordHash` sein
	$currentHashInstance = $this->getHashInstance( $passwordHash );
	// Könnte z.B. `TYPO3\CMS\Core\Crypto\PasswordHashing\BcryptPasswordHash` sein
	$expectedHashInstance = GeneralUtility::makeInstance(PasswordHashFactory::class)->getDefaultHashInstance( $loginType );
	return get_class($currentHashInstance) != get_class($expectedHashInstance);
}