WordPress Infinite Scroll – Ajax Load More <= 5.5.3 - Cross-Site Request Forgery to PHAR Deserialization

The WordPress Infinite Scroll – Ajax Load More plugin for WordPress is vulnerable to deserialization of untrusted input via the 'alm_repeaters_export' parameter in versions up to, and including 5.5.3. This makes it possible for unauthenticated users to call files using a PHAR wrapper, granted they can trick a site administrator into performing an action such as clicking on a link, that will deserialize and call arbitrary PHP Objects that can be used to perform a variety of malicious actions granted a POP chain is also present. It also requires that the attacker is successful in uploading a file with the serialized payload.

The attempt arrives as an ordinary request to Ajax Load More: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: Ajax Load More 5.5.4 closes this, and updating the plugin is the step that ends it.

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