Authenticated arbitrary file write via unsanitized character_name

Path traversal in SillyTavern before 1.17.0 allows remote authenticated users to write files outside the intended chats directory. The import handler embeds character_name in a destination filename, joins it beneath the chats path without sanitization, and writes or copies the uploaded chat. A valid session and CSRF token are required; exploitation places attacker-chosen content at any path writable by the service account.