Categories Images <= 3.3.1 - Authenticated (Contributor+) Stored Cross-Site Scripting
Description
The Categories Images plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 3.3.1 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
CVSS Vector Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:NTechnical Details
<=3.3.1What Changed in the Fix
Changes introduced in v3.3.2
Source Code
WordPress.org SVNshortcode: z_taxonomy_list` - Attributes (from readme): `term_id`, `size`, `link`, `taxonomy`, `style`, `columns`, `show_name`. Let's use `z_taxonomy_list` and the `style` attribute as the example. *Payload:* `grid" onmouseover="alert(1)"` *Expected Output:* `<div c…
Show full research plan
shortcode: z_taxonomy_list - Attributes (from readme):term_id, size, link, taxonomy, style, columns, show_name`.
Let's use `z_taxonomy_list` and the `style` attribute as the example.
*Payload:* `grid" onmouseover="alert(1)"`
*Expected Output:* `<div class="zci-list zci-grid" onmouseover="alert(1)" ...>`
Wait, I should check `z_taxonomy_image_shortcode`.
`[z_taxonomy_image link="javascript:alert(1)"]`
If the code is `<a href="<?php echo $atts['link']; ?>">`, then clicking the image triggers XSS.
If the code is `<img src="..." alt="<?php echo $atts['alt']; ?>">`, then `alt=' " onerror=alert(1) '` triggers it.
Let's check the code snippet one more time.
It shows `z_taxonomy_image_shortcode` is registered.
*Plan Detail:*
I will use the `[z_taxonomy_image]` shortcode with the `size` attribute for a direct, non-click XSS.
Payload: `size=' " onerror="alert(1)" '`
Assuming the code does: `<img src="..." class="attachment-[size]">`.
*Refined plan for the agent:*
1.
Summary
The Categories Images plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the [z_taxonomy_image] shortcode in versions up to 3.3.1. This occurs because the plugin fails to sanitize and escape attributes like 'alt', 'class', 'width', and 'title' before outputting them in an HTML image tag, allowing contributor-level users to execute arbitrary JavaScript in the context of a victim's browser.
Vulnerable Code
// categories-images.php if(is_array($attr)) { if(!empty($attr['class'])) $image_attr .= ' class="'.$attr['class'].'" '; // Line 374 if(!empty($attr['alt'])) $image_attr .= ' alt="'.$attr['alt'].'" '; // Line 376 if(!empty($attr['width'])) $image_attr .= ' width="'.$attr['width'].'" '; // Line 378 if(!empty($attr['height'])) $image_attr .= ' height="'.$attr['height'].'" '; // Line 380 if(!empty($attr['title'])) $image_attr .= ' title="'.$attr['title'].'" '; // Line 382 } $taxonomy_image = '<img src="'.$taxonomy_image_url.'" '.$image_attr.'/>'; // Line 384 // ... later in the same function if ($echo) echo $taxonomy_image; // Line 394
Security Fix
@@ -371,17 +369,17 @@ $image_attr = ''; if(is_array($attr)) { if(!empty($attr['class'])) - $image_attr .= ' class="'.$attr['class'].'" '; + $image_attr .= ' class="'.esc_attr($attr['class']).'" '; if(!empty($attr['alt'])) - $image_attr .= ' alt="'.$attr['alt'].'" '; + $image_attr .= ' alt="'.esc_attr($attr['alt']).'" '; if(!empty($attr['width'])) - $image_attr .= ' width="'.$attr['width'].'" '; + $image_attr .= ' width="'.esc_attr($attr['width']).'" '; if(!empty($attr['height'])) - $image_attr .= ' height="'.$attr['height'].'" '; + $image_attr .= ' height="'.esc_attr($attr['height']).'" '; if(!empty($attr['title'])) - $image_attr .= ' title="'.$attr['title'].'" '; + $image_attr .= ' title="'.esc_attr($attr['title']).'" '; } - $taxonomy_image = '<img src="'.$taxonomy_image_url.'" '.$image_attr.'/>'; + $taxonomy_image = '<img src="'.esc_url($taxonomy_image_url).'" '.$image_attr.'/>'; } } else{ @@ -389,7 +387,7 @@ } if ($echo) - echo $taxonomy_image; + echo wp_kses_post($taxonomy_image); else return $taxonomy_image; }
Exploit Outline
The exploit requires an attacker with at least Contributor-level privileges, as they need the ability to edit posts or pages where shortcodes can be processed. 1. The attacker creates or edits a post. 2. The attacker inserts the [z_taxonomy_image] shortcode, providing a malicious payload into one of the HTML attributes processed by the function (such as 'alt', 'class', or 'title'). 3. Payload Example: `[z_taxonomy_image alt='" onmouseover="alert(document.domain)"']`. 4. When the post is saved and then viewed by any user (including an Administrator), the unescaped attribute breaks out of the HTML <img> tag, injecting the event handler. 5. The JavaScript executes when the victim's mouse interacts with the image.
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