full-disclosure - [FD] CSRF and arbitrary file deletion in BuddyPress Activity Plus 1.5 (WordPress plugin)

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Message-ID: <d8c3b16ab4aadcb40d2c6e7a39e970b2@security.dxw.com>
Date: Tue, 14 Jul 2015 17:07:58 +0000
From: dxw Security <security@....com>
To: fulldisclosure@...lists.org
Subject: [FD] CSRF and arbitrary file deletion in BuddyPress Activity Plus
	1.5 (WordPress plugin)

Details
================
Software: BuddyPress Activity Plus
Version: 1.5
Homepage: http://wordpress.org/plugins/buddypress-activity-plus/
Advisory report: https://security.dxw.com/advisories/csrf-and-arbitrary-file-deletion-in-buddypress-activity-plus-1-5/
CVE: Awaiting assignment
CVSS: 8.5 (High; AV:N/AC:L/Au:N/C:N/I:P/A:C)

Description
================
CSRF and arbitrary file deletion in BuddyPress Activity Plus 1.5

Vulnerability
================
An attacker can delete any file the PHP process can delete.
For this to happen, a logged-in user would have to be tricked into clicking on a link controlled by the attacker. It is easy to make these links very convincing.

Proof of concept
================
Ensure your PHP user can do maximum damage:
sudo chown www-data:www-data /var/vhosts/my-wordpress-site
Visit a page containing this as a logged-in user and click submit:
<form method=\"POST\" action=\"http://localhost/wp-admin/admin-ajax.php\">
  <input type=\"text\" name=\"action\" value=\"bpfb_remove_temp_images\">
  <input type=\"text\" name=\"data\" value=\"bpfb_photos[]=../../../../wp-config.php\">
  <input type=\"submit\">
</form>
If the server is set up so that the php user has more restricted permissions, then an attacker will at least be able to delete files from the uploads directory.
Note that you can also delete as many things as you like at once – $_POST[‘data’] is run through parse_str() which parses it as a query string, so just keep adding “&bpfb_photos[]=path/to/file” to the end until you have all known files.
There is an identical attack available only when BP Group Documents is also installed. Just replace “bpfb_remove_temp_images” with “bpfb_remove_temp_documents” and in data replace “bpfb_photos” with “bpfb_documents”.

Mitigations
================
Upgrade to version 1.6.2 or later
If this is not possible, ensure that the PHP user on the server does not have permission to delete files like wp-config.php.

Disclosure policy
================
dxw believes in responsible disclosure. Your attention is drawn to our disclosure policy: https://security.dxw.com/disclosure/

Please contact us on security@....com to acknowledge this report if you received it via a third party (for example, plugins@...dpress.org) as they generally cannot communicate with us on your behalf.

This vulnerability will be published if we do not receive a response to this report with 14 days.

Timeline
================

2013-08-22: Discovered
2015-07-13: Reported to vendor via contact form at https://premium.wpmudev.org/contact/
2015-07-13: Requested CVE
2015-07-13: Vendor responded
2015-07-14: Vendor reported issue fixed
2015-07-14: Published

Discovered by dxw:
================
Tom Adams
Please visit security.dxw.com for more information.

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