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 product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.