gif_outputAsJpeg in phpThumb through 1.7.23 allows phpthumb.gif.php OS Command Injection via a crafted parameter value. This is fixed in 1.7.23-202506081709.
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.