PhastPress < 3.8 - Unauthenticated Arbitrary File Read via Null Byte Injection

Description

The plugin is vulnerable to Unauthenticated Arbitrary File Read via null byte injection 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.