The PhastPress plugin for WordPress is vulnerable to Unauthenticated Arbitrary File Read via null byte injection in all versions up to, and including, 3.7. This is due to a discrepancy between the extension validation in getExtensionForURL() which operates on URL-decoded paths, and appendNormalized() which strips everything after a null byte before constructing the filesystem path. This makes it possible for unauthenticated attackers to read arbitrary files from the webroot, including wp-config.php, by appending a double URL-encoded null byte (%2500) followed by an allowed extension (.txt) to the file path.
Exploitability
AV:NAC:LPR:NUI:NScope
S:UImpact
C:HI:HA:H9.8/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HOther