Description

Deserialization of Untrusted Data vulnerability in PressTigers Simple Event Planner simple-event-planner allows Object Injection.This issue affects Simple Event Planner: from n/a through 1.5.7.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-10-05T20:17:29.447Z",
  "pubdate": "2026-10-05T20:17:29.447Z",
  "executiveSummary": "The Simple Event Planner plugin for WordPress, versions 1.5.7 and earlier, contains a critical Deserialization of Untrusted Data vulnerability.\nThis flaw allows remote, unauthenticated attackers to perform PHP Object Injection by passing malicious serialized data to the application.\nSuccessful exploitation permits arbitrary code execution, unauthorized data modification, or denial-of-service, depending on the availability of POP (Property Oriented Programming) chains within the application's environment.\nThe vulnerability stems from improper validation of user-supplied data before it is passed to an unserialization function, a common pattern that enables attackers to manipulate object state and trigger unintended behavior.\nGiven the severity, this vulnerability presents a high risk to organizational security, potentially leading to full site compromise if the plugin is active on a system with vulnerable gadgets in the codebase or dependencies.\nImmediate remediation is necessary to prevent exploitation by threat actors.",
  "technicalDetails": "The core of this vulnerability is an insecure deserialization flaw within the Simple Event Planner plugin. Deserialization is the process of converting a stored or transmitted byte stream back into a complex object in the application's memory. When an application utilizes functions such as unserialize() on untrusted, user-controlled input, it allows an attacker to dictate the class type and properties of the object being instantiated.\nIn the context of the Simple Event Planner plugin, the application fails to verify the integrity or origin of the serialized input before processing it. By crafting a specifically formatted serialized payload, an attacker can instantiate existing classes within the WordPress environment or its dependencies.\nIf the application context contains 'gadget chains'—a sequence of magic methods (such as __destruct(), __wakeup(), or __toString()) present in standard classes—the attacker can chain these method calls together upon the destruction or manipulation of the injected object.\nThe attack flow proceeds as follows: 1) The attacker identifies a vulnerable entry point where serialized data is accepted via HTTP request parameters. 2) The attacker generates a malicious payload containing a serialized object structure tailored to leverage existing POP gadgets. 3) The payload is transmitted to the vulnerable plugin component. 4) The plugin passes the attacker-controlled input to an unserialization function. 5) The PHP engine reconstructs the object, inadvertently executing the attacker's defined gadget chain. 6) The final impact is determined by the gadgets used; this frequently results in Remote Code Execution (RCE) via functions like eval() or system(), file system operations, or database interaction.\nBecause the input is processed during the handling of incoming requests, this vulnerability is exploitable over the network without requiring authentication. The exploit surface covers all versions of Simple Event Planner from n/a through 1.5.7. The scope of the post-exploitation impact is limited only by the permissions of the web server process and the availability of executable code within the application's namespace, effectively allowing an attacker to achieve full control over the WordPress instance."
}