SI 2FA Login Security

Basically, it's to do with securing your logins, so that there's more than one link in the chain needing to be broken before an unwanted intruder can get in your website. By default, your WordPress accounts are protected by only one thing: your password. If that's broken, then everything's wide open. "MFA Factor Auth" means adding a second requirement. Usually, this is a code that comes to a device you own (e.g. phone, tablet) - so, someone can't get into your website without getting hold of your device. You can get a longer answer from Wikipedia.

Since "SI 2FA Login Security" just means "a second something is necessary to get in", this answer depends upon the particular set-up. In the most common case, a numeric code is shown on your phone, tablet or other device. This code be sent via an Authenticator; this then depends on the mobile phone network working. This plugin does not uses that method. Instead, it uses a standard mathematical algorithm to generate codes that are only valid once each, or for only for 30 seconds (depending on which algorithm you choose). Your phone or tablet can know the code after it has been set up once (often, by just scanning a bar-code off the screen).

This depends on your particular make of phone, and your preferences. Google have produced a popular app called "Google Authenticator", which is a preferred option for many people because it is easy to use and can be set up via just scanning a bar code off your screen - follow this link, and ignore the first paragraph that is talking about 2FA on your Google account (rather than being relevant to this plugin).

Many and various devices and programs can generate the codes. One option is an add-on for your web browser; for example, here are some apps and add-ons for Google Chrome. Wikipedia lists various programs for different computers. If you cannot get in and need to disable mfa-factor authentication, then add this to your wp-config.php file, using FTP or the file manager in your hosting control panel: define('SI2FLOSE_FACTOR_DISABLE', true);

[si2flose_twofactor_user_settings]

You have a password manager extension installed in your web browser, with the correct password entered in it. It has automatically replaced your wrong password with the right one from its saved store. This behaviour has been observed and confirmed by several users. You can verify it by using the web developer tools in your browser to look at the HTTP data sent to WordPress, and observe which password is actually in it. You can also open a fresh web browser with no such extension in it to re-test. Note that the two factor authentication plugin has no mechanism to compare or approve passwords; this is done by WordPress core. If the wrong password is sent, then this is handled by WordPress, and the login will not proceed.