June 2024 brought a new security alert for Moodle administrators: CVE-2024-48897 highlights a flaw that could let users edit or delete RSS feeds they shouldn't have access to. Let's look at what this means, see how it works, explore the fix, and make sure your Moodle site is safe.

What is Moodle and What's at Risk?

Moodle is a popular open-source learning platform used by schools, universities, and companies worldwide. It lets users add RSS feeds to bring in news and content updates.

The vulnerability:
Without proper permission checks, a logged-in user might be able to edit or delete any RSS feeds—even those created by other users.

This could allow unwanted changes, deleted news blocks, or even tricks to show the wrong information in courses or dashboards.

Where is the Problem?

In Moodle, RSS feeds can be managed through blocks (like *Remote RSS feeds* block). Each feed is stored in a table such as block_rss_client. When a user edits or deletes a feed, Moodle *should* check if the user actually owns that feed or has the right permissions.

But due to missing or incomplete checks, any authenticated user could send crafted requests to edit or delete another user's RSS feed.

Vulnerable Function (Example Illustration)

Often, issues happen in PHP scripts like editfeed.php or within block code that handles RSS feed management.

Here’s a simplified look at what might go wrong

// editfeed.php
require_login();
$feedid = required_param('id', PARAM_INT);

// Missing: Should check if the current user is the feed's owner!
// Existing code:
$DB->update_record('block_rss_client', $updatedfeed);

// User A can now edit feed created by User B by guessing/changing the feed ID!

The check that’s missing is something like

$feed = $DB->get_record('block_rss_client', ['id' => $feedid]);
// This SHOULD be here:
if ($feed->userid !== $USER->id && !has_capability('moodle/site:manageblocks', $context)) {
    print_error('You do not have permission to edit this feed.');
}

How Could This Be Exploited?

Attack scenario example:

User A guesses or enumerates feed IDs to find feeds they do not own.

3. User A submits an HTTP request (perhaps tweaking a form or using a tool like Burp Suite) to edit or delete the targeted feed.

Because Moodle isn’t verifying ownership, the request succeeds.

Effect:
User A just edited or deleted content that didn’t belong to them.

Real Exploit: Step-by-Step

Below is a walkthrough:

`

POST /blocks/rss_client/editfeed.php?id=234

References and Original Sources

- CVE-2024-48897 NVD Entry
- Moodle Security Announcements
- Remote RSS Feeds User Permissions Docs

How to Fix It?

Moodle's fix:
They added checks to be sure users can only edit or delete feeds they created, unless they have specific admin permissions.

Simple secure version

// Secure editfeed.php
require_login();
$feedid = required_param('id', PARAM_INT);

$feed = $DB->get_record('block_rss_client', array('id'=>$feedid));

if ($feed->userid != $USER->id && !has_capability('block/rss_client:managefeeds', context_system::instance())) {
    print_error('You do not have permission to edit this feed.');
}

// Continue with edit/delete logic...

To check if you’re affected

- You must be running a Moodle version older than the patched release mentioned in the official advisory (link hypothetical—replace with real once available).

Try editing a feed from another user as described above.

Update your Moodle install:
At the time of writing, update to the latest Moodle release to receive the fix. Double-check that block/rss capability assignments are as minimal as possible in your roles and permissions settings.

Review user roles and permissions: Only admins should have the ability to manage all RSS feeds.

3. Test: Try the edit/delete exploit as above with non-admins to confirm the fix.

Final Thoughts

*CVE-2024-48897 is a reminder that even simple features like RSS feed blocks need careful permission checks. If you run Moodle, keep it up to date — and always assume that users might try things they shouldn’t be allowed to. Stay safe, and happy teaching!*

Timeline

Published on: 11/18/2024 12:15:18 UTC
Last modified on: 11/20/2024 14:48:25 UTC