A recently uncovered critical vulnerability in the Spiffy Calendar WordPress plugin - CVE-2024-0855 - has left numerous websites and users exposed to potential attacks. The vulnerability is present in Spiffy Calendar versions prior to 4.9.9 and allows any user to create an event and maliciously attribute the event_author parameter to a different user, ultimately giving the false impression that the event was created by a Contributor+ user. In this long read, we will provide in-depth details on this vulnerability, including code snippets, exploit details, and links to original references.

Vulnerability Overview

The Spiffy Calendar plugin is widely used for handling events and appointments on WordPress websites. This vulnerability allows any user with access to the plugin's event creation functionality to manipulate the event_author parameter. By altering the parameter, the attacker can deceive both users and administrators into believing the event was created by an authoritative figure.

Here is an example of a PHP code snippet from the vulnerable Spiffy Calendar plugin

function create_new_event() {
    global $wpdb;
    $event_author = intval($_POST['event_author']);
    
    // Insert event into database
    $wpdb->insert( ... );
}

As you can see, the event_author parameter is fetched directly from the POST request without any form of validation or permission check. This makes it possible for an attacker to create an event and alter the event_author parameter to match the ID of another user, such as an admin or contributor.

Exploit Details

Due to the lack of proper validation, an attacker can submit a new event with manipulated event_author data. Here's an example of a malformed HTTP request that exploits this vulnerability:

POST /wp-admin/admin-post.php HTTP/1.1
Host: example.com
Content-Type: application/x-www-form-urlencoded

action=spiffy_create_event&event_author=2&event_title=Fake+Event ...

In this example, the attacker sends a POST request to the /wp-admin/admin-post.php page with manipulated data for the event_author parameter. This allows the attacker to create an event that appears to be authored by a user with the ID of 2.

This vulnerability can have several detrimental effects

1. Deception: Visitors and administrators of the website believe that the events were created by credible authorities, making them susceptible to disinformation or the unintended allocation of resources.

2. Reputation damage: If a website is found to be hosting deceptive events, its credibility and reputation could be irreparably harmed.

3. Legal consequences: Fraudulent event attribution can lead to legal ramifications for the website owner and administrators if events result in the loss or harm to users.

Mitigation

To mitigate this vulnerability, users are urged to update their Spiffy Calendar plugin to version 4.9.9 or later, which includes a patch for the CVE-2024-0855 vulnerability. The fixed version of the plugin has additional checks to ensure that users cannot manipulate the event_author parameter when creating events.

function create_new_event() {
    global $wpdb;
    
    // Check if current user has permission to create events as another user
    if (current_user_can('promote_users')) {
        $event_author = intval($_POST['event_author']);
    } else {
        $event_author = get_current_user_id();
    }
    
    // Insert event into database
    $wpdb->insert( ... );
}

In this fixed code snippet, the plugin checks if the current user has the necessary permissions to create an event on behalf of another user. If they do not possess the required permissions, the event_author parameter is set to the ID of the current user, preventing unauthorized manipulation.

Original References

1. CVE-2024-0855 entry on the National Vulnerability Database (NVD): https://nvd.nist.gov/vuln/detail/CVE-2024-0855

2. Spiffy Calendar WordPress plugin changelog: https://wordpress.org/plugins/spiffy-calendar/#developers

Conclusion

In conclusion, the CVE-2024-0855 vulnerability is a critical issue in the Spiffy Calendar WordPress plugin that allows any user to create deceptive events by altering the event_author parameter. Site administrators should update the plugin to version 4.9.9 or later to mitigate this vulnerability. Additionally, users should remain vigilant in verifying the authenticity of events posted on websites using the Spiffy Calendar plugin.

Timeline

Published on: 02/27/2024 09:15:37 UTC
Last modified on: 08/08/2024 21:35:01 UTC