Recent Yii2 Update Via Composer Breaks Advanced Template User Class

[size="1"]note - I originally thought I was having issues with "composer update --prefer-dist" but this is not the case. Please move this thread to the appropriate location, thanks[/size]

This morning I was updating my vendor packages for the Yii2 Advanced Application Template I

am using. I tried to log into my CMS, and was met with this error:

Class 'yii\helpers\Security' not found

 in /var/www/mypath/common/models/User.php


     * Validates password


     * @param  string  $password password to validate

     * @return boolean if password provided is valid for current user


    public function validatePassword($password)


        return Security::validatePassword($password, $this->password_hash);


I tried changing the namespace inclusion to "yii\base\Security" but this just brought about new errors pertaining to missing properties of my class User.

Is there a way I can catch the User class that comes with the Advanced Application Template up to date with these recent framework changes? Should I not be using this class anymore? Is there a new go-to option for a User class for the Advanced Application Template I should be using? How should I resolve this, besides create a new User model?