CVE-2019-25147 in Pretty Links Plugin
Summary
by MITRE • 06/07/2023
The Pretty Links plugin for WordPress is vulnerable to Stored Cross-Site Scripting via various IP headers as well as the referer header in versions up to, and including, 2.1.9 due to insufficient input sanitization and output escaping in the track_link function. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 07/05/2023
The Pretty Links plugin for WordPress represents a widely used tool for managing and tracking URL redirects within WordPress environments. This particular vulnerability exists in versions up to and including 2.1.9 where the track_link function fails to properly sanitize or escape user-supplied input from HTTP headers. The flaw specifically targets several IP headers and the referer header, which are commonly used by web applications to track visitor information and routing data. These headers are typically automatically populated by web browsers and proxy servers, making them susceptible to manipulation by attackers who can inject malicious scripts directly into the header values.
The technical implementation of this vulnerability stems from inadequate input validation within the plugin's core tracking mechanism. When the track_link function processes incoming requests, it directly incorporates data from HTTP headers without sufficient sanitization measures. This creates a classic stored cross-site scripting condition where malicious payloads can be persisted in the application's data storage and executed whenever legitimate users access affected pages. The vulnerability operates at the application layer and requires no authentication from attackers, making it particularly dangerous in environments where the plugin is widely deployed.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, and data exfiltration. When unauthenticated users visit pages that contain the injected scripts, the malicious code executes in their browser context, potentially allowing attackers to steal cookies, capture form data, or redirect users to malicious sites. The stored nature of the vulnerability means that once injected, the malicious scripts remain persistent until manually removed from the plugin's tracking system, creating ongoing security risks for all users who encounter the compromised content.
Mitigation strategies for this vulnerability should focus on immediate patching of the Pretty Links plugin to version 2.1.10 or later, which contains the necessary sanitization fixes. Organizations should also implement network-level protections such as web application firewalls that can detect and block suspicious header values, though this approach is less reliable than proper input sanitization. Security teams should conduct comprehensive audits of all WordPress installations to identify potentially compromised systems and monitor for unauthorized modifications to plugin files. The vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and represents a technique commonly categorized under ATT&CK tactic TA0001 (Initial Access) and technique T1190 (Exploit Public-Facing Application) in the MITRE ATT&CK framework. Organizations should also consider implementing Content Security Policy headers as an additional defense-in-depth measure to limit script execution capabilities within their WordPress environments.