fishaudio/Bert-VITS2 Limited File Write in webui_preprocess.py generate_config function

Bert-VITS2 is the VITS2 Backbone with multilingual bert. User input supplied to the data_dir variable is concatenated with other folders and used to open a new file in the generate_config function, which leads to a limited file write. The issue allows for writing /config/config.json file in arbitrary directory on the server. If a given directory path doesn’t exist, the application will return an error, so this vulnerability could also be used to gain information about existing directories on the server. This affects fishaudio/Bert-VITS2 2.3 and earlier.