The core view rendering method View::renderPhpFile() calls extract($_params_, EXTR_OVERWRITE) before the require statement that includes the view file. A caller-controlled parameter named _file_ in the $params array overwrites the internal local variable that specifies which file is included — enabling a Local File Inclusion primitive.
Impact
Local File Inclusion (arbitrary file read via non-PHP files)
Potential RCE if attacker can write PHP files via a separate primitive