CVE-2026-39580: WordPress Micdrop theme <= 1.3.1 - PHP Object Injection vulnerability

Synopsis

PHP Object Injection is a vulnerability in the Micdrop WordPress theme (versions 1.3.1 and earlier) where an attacker sends a crafted, serialized payload to the application over the network without any authentication. If a suitable "POP chain" (a sequence of existing PHP class methods that the injected object triggers) is present in the codebase or any loaded plugin, a successful attacker can read sensitive data, modify stored content, or disrupt the site entirely. HarborGuard is tracking this advisory and will make a patched-image rebuild available the moment an upstream fix is published.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the WordPress site over the network; the vulnerable deserialization endpoint is exposed via standard HTTP/HTTPS requests.

• AuthenticationNot required

  No account or session token is needed; the injection can be triggered by an anonymous, unauthenticated request.

• Victim interactionNot required

  No user action is required; the attacker sends the malicious payload directly to the application without involving any victim.

• Attack complexityDetail

  Attack complexity is high, meaning exploitation depends on environmental factors such as the presence of a usable POP chain in the theme or any co-installed plugin, making reliable exploitation condition-dependent.

Blast Radius

• Reads confidential data stored on the site, including database credentials, session tokens, and user records, if a POP chain enabling file or database read is present.
• Modifies or deletes persisted content such as posts, plugin configuration, and user accounts if a POP chain enabling write operations is available.
• Crashes or renders the WordPress application unavailable by triggering destructors that exhaust memory, corrupt state, or delete critical files.
• Achieves remote code execution on the host container if the available POP chain leads to a file-write or eval-equivalent operation.