CVE-2026-97246 in Image Optimizer Plugin
Summary
by MITRE • 09/30/2026
Subscriber PHP Object Injection in ShortPixel Image Optimizer <= 6.5.5 versions.
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Analysis
by VulDB Data Team • 09/30/2026
The vulnerability identified as Subscriber PHP Object Injection within the ShortPixel Image Optimizer plugin, affecting versions up to and including 6.5.5, represents a critical security flaw rooted in improper handling of user-supplied input during object deserialization processes. This type of vulnerability allows an attacker to inject malicious serialized data into the application's execution flow, which is then unserialized by the PHP engine without adequate validation or sanitization. The core technical issue lies in the lack of strict typing and integrity checks on data that originates from external sources, such as HTTP requests or database entries managed through administrative interfaces. When the plugin processes this unsanitized input to reconstruct a PHP object, it inadvertently instantiates classes with properties controlled by the attacker, leading to unintended side effects within the application's runtime environment.
From an architectural perspective, this flaw aligns closely with CWE-502, which describes Deserialization of Untrusted Data. The vulnerability typically manifests when the plugin accepts parameters that are directly passed into functions like unserialize() or similar mechanisms used for restoring object states from storage. Because PHP objects can contain references to other classes and methods, an attacker who controls the serialized payload can manipulate these internal structures. This manipulation is not merely about data corruption but involves exploiting the lifecycle of instantiated objects. If the vulnerable code path does not restrict which classes can be deserialized or verify that the incoming data matches expected schemas, it opens a gateway for arbitrary object instantiation.
The operational impact of this vulnerability is severe due to its potential for Remote Code Execution (RCE). By crafting specific serialized payloads, an attacker can trigger magic methods such as __destruct(), __wakeup(), or __toString() within instantiated classes. These methods often contain logic that interacts with the file system, executes shell commands, or performs database operations. In the context of a WordPress plugin like ShortPixel Image Optimizer, which handles media files and server configurations, successful exploitation could allow an attacker to write malicious scripts to the web directory, read sensitive configuration files containing database credentials, or execute arbitrary system commands on the host server. This effectively compromises the entire website infrastructure, leading to data breaches, defacement, or the use of the compromised server as a pivot point for further attacks against internal networks.
This vulnerability is also associated with CWE-915, Improperly Controlled Modification of Dynamically-Determined Object Attributes, and maps directly to MITRE ATT&CK technique T1059, Command and Scripting Interpreter, specifically under sub-techniques related to PHP execution if the deserialization leads to code execution. The attack vector typically requires at least low privileges within WordPress, such as a subscriber or contributor role, depending on how the vulnerable function is exposed. However, in many cases involving object injection, even lower privilege levels can be sufficient if the plugin does not enforce strict capability checks before processing input for deserialization purposes.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The primary solution is to upgrade the ShortPixel Image Optimizer plugin to a version greater than 6.5.5, where the developers have presumably implemented proper validation mechanisms or removed the vulnerable code paths. For organizations unable to update immediately due to compatibility constraints, temporary mitigations include restricting file upload permissions and ensuring that any custom code interacting with the plugin's API performs strict input sanitization using allowlists for expected data types rather than relying on type coercion alone. Additionally, implementing a Web Application Firewall (WAF) rule set capable of detecting anomalous serialized strings or known gadget chain patterns can provide an additional layer of defense against exploitation attempts in production environments.