Call to the scrypt_enc() function in HHVM can lead to heap corruption by using specifically crafted parameters (N, r and p). This happens if the parameters are configurable by an attacker for instance by providing the output of scrypt_enc() in a context where Hack/PHP code would attempt to verify it by re-running scrypt_enc() with the same parameters. This could result in information disclosure, memory being overwriten or crashes of the HHVM process. This issue affects versions 4.3.0, 4.4.0, 4.5.0, 4.6.0, 4.7.0, 4.8.0, versions 3.30.5 and below, and all versions in the 4.0, 4.1, and 4.2 series.

Cross-site scripting (XSS) vulnerability in the WddxPacket::recursiveAddVar function in HHVM (aka the HipHop Virtual Machine) before 3.5.0 allows remote attackers to inject arbitrary web script or HTML via a crafted string to the wddx_serialize_value function.