SillyTavern is a locally installed user interface that allows users to interact with text generation large language models, image generation engines, and text-to-speech voice models. Prior to 1.18.0, POST /api/extensions/delete endpoint accepts extensionName: "." which bypasses sanitize-filename validation, causing the entire user extensions directory to be recursively deleted. No authentication is required in the default configuration. This vulnerability is fixed in 1.18.0.