Allow Multiple Accounts vs Host Header Injection Fix

Allow multiple user accounts to be created, registered, and updated having the same email address. By default, WordPress only allows a specific email address to be used for a single user account. This plugin removes that restriction. The plugin’s settings page (accessed via Users -> Multiple Accounts or via the Settings link next to the plugin on the Manage Plugins page) provides the ability to allow only certain email addresses the ability to have multiple accounts (such as if you only want admins to have that ability; by default all email addresses can be used more than once). You may also specify a limit to the number of accounts an email address can have (by default there is no limit). The settings page also provides a table listing all user accounts that share email addresses (see screenshot). Compatible with Multisite and BuddyPress as well. Links: Plugin Homepage | Plugin Directory Page | Author Homepage Template Tags The plugin provides three optional template tags for use in your theme templates. Functions Returns a count of the number of users associated with the given email. Returns the users associated with the given email. Returns a boolean indicating if the given email is associated with more than one user account. Arguments $email (string) An email address. Filters The plugin exposes three filters for hooking. Typically, customizations utilizing these hooks would be put into your active theme’s functions.php file, or used by another plugin. c2c_count_multiple_accounts (filter) The ‘c2c_count_multiple_accounts’ hook allows you to use an alternative approach to safely invoke c2c_count_multiple_accounts() in such a way that if the plugin were deactivated or deleted, then your calls to the function won’t cause errors in your site. Arguments: same as for c2c_count_multiple_accounts() Example: Instead of: Do: c2c_get_users_by_email (filter) The ‘c2c_get_users_by_email’ hook allows you to use an alternative approach to safely invoke c2c_get_users_by_email() in such a way that if the plugin were deactivated or deleted, then your calls to the function won’t cause errors in your site. Arguments: same as for c2c_get_users_by_email() Example: Instead of: Do: c2c_has_multiple_accounts (filter) The ‘c2c_has_multiple_accounts’ hook allows you to use an alternative approach to safely invoke c2c_has_multiple_accounts() in such a way that if the plugin were deactivated or deleted, then your calls to the function won’t cause errors in your site. Arguments: same as for c2c_has_multiple_accounts() Example: Instead of: Do:

👉 Enables custom headers for WP email notifications 👉 Also provides a “set it and forget it” security fix for WP < 5.5 👉 Uses only 50KB of code, so super lightweight, fast, and effective Important As of WordPress 5.5, this plugin no longer is necessary to fix the host-header security issue reported in Ticket #25239 finally is fixed, and mentioned in this post WordPress 5.5 Beta 4. Thank You WordPress devs! Is this plugin still useful? Yes, it enables you to choose the “From”, “Name”, and “Return-Path” headers for all WP notification emails. And for versions of WordPress less than 5.5, this plugin continues to fix the host-header injection security issue. Features This simple plugin does three things: Sets custom From, Name, and Return-Path for WP notifications Fixes a security vulnerability in WordPress versions < 5.5 Fixes a bug where invalid email addresses may be generated (in WordPress versions < 5.5) Choose from the following options: Use WordPress defaults (insecure for WP < 5.5) Use “Email Address” from WP General Settings Use a custom name and address Plus there is an option to use the specified From address as the Return-Path header. Why? The security issue fixed by this plugin has been known about since way back in WordPress version 2.3. There has been some talk about fixing, but nothing has been implemented. While the issue does not affect all sites, it does affect a good percentage of them, including some of my own projects. So, not wanting to get hacked, I decided to write my own solution. Hopefully this issue gets fixed in a future version of WordPress, and this plugin will become unnecessary. As a bonus, setting an explicit From address resolves a long-standing bug whereby an invalid email address is generated under the following conditions: A “From” address is not set, And the $_SERVER['SERVER_NAME'] is empty So by explicitly setting a “From” address, we prevent this bug from happening. Security Issue What is the security issue addressed by this plugin? Follows is a quick summary. To learn more in-depth, check out the resources linked in the next section. WP uses $_SERVER['SERVER_NAME'] to set the “From” header in email notifications This includes sensitive email notifications like password resets and user registration In some cases, an attacker could modify the “From” header and intercept the email Using the intercepted email, an attacker could gain access to your site and wreak havoc More Infos This security vulnerability is well-known and has been around for a looong time. To learn more, check out these articles: WP Core Trac Ticket Exploit Box Info Exploit Database Privacy This plugin does not collect or store any user data. It does not set any cookies, and it does not connect to any third-party locations. Thus, this plugin does not affect user privacy in any way. Host Header Injection Fix is developed and maintained by Jeff Starr, 15-year WordPress developer and book author. Support development I develop and maintain this free plugin with love for the WordPress community. To show support, you can make a donation or purchase one of my books: The Tao of WordPress Digging into WordPress .htaccess made easy WordPress Themes In Depth Wizard’s SQL Recipes for WordPress And/or purchase one of my premium WordPress plugins: BBQ Pro – Blazing fast WordPress firewall Blackhole Pro – Automatically block bad bots Banhammer Pro – Monitor traffic and ban the bad guys GA Google Analytics Pro – Connect WordPress to Google Analytics Head Meta Pro – Ultimate Meta Tags for WordPress REST Pro Tools – Awesome tools for managing the WP REST API Simple Ajax Chat Pro – Unlimited chat rooms USP Pro – Unlimited front-end forms Links, tweets and likes also appreciated. Thank you! 🙂