AstrBot has an arbitrary file read vulnerability in function _encode_image_bs64

AstrBot Project v3.5.22 has an arbitrary file read vulnerability in function _encode_image_bs64. Since the _encode_image_bs64 function defined in entities.py opens the image specified by the user in the request body and returns the image content as a base64-encoded string without checking the legitimacy of the image path, attackers can construct a series of malicious URLs to read any specified file, resulting in sensitive data leakage.