SillyTavern: Path Traversal in `/api/chats/export` and `/api/chats/delete` allows arbitrary file read/delete within user data root

Summary

A Path Traversal vulnerability in chat endpoints allows an authenticated attacker to read and delete arbitrary files under their user data root (for example secrets.json and settings.json) by supplying avatar_url="..".

Details

The input validator used by avatar_url blocks only / and NUL bytes, but does not block traversal segments like ...

Evidence:
- Weak validator regex (does not reject ..):
<https://github.com/SillyTavern/SillyTavern/blob/b7bb8be35a5c779b4db12a4a5b94d7e49096071c/src/middleware/validateFileName.js#L24-L27>
- Vulnerable delete path construction:
<https://github.com/SillyTavern/SillyTavern/blob/b7bb8be35a5c779b4db12a4a5b94d7e49096071c/src/endpoints/chats.js#L575-L577>
- Vulnerable export path construction:
<https://github.com/SillyTavern/SillyTavern/blob/b7bb8be35a5c779b4db12a4a5b94d7e49096071c/src/endpoints/chats.js#L595-L598>
- Endpoint auth context (authenticated user access):
<https://github.com/SillyTavern/SillyTavern/blob/b7bb8be35a5c779b4db12a4a5b94d7e49096071c/src/server-main.js#L239>

Because avatar_url=".." is accepted, path.join(<user>/chats, "..") resolves to <user>/, enabling direct access to files outside the chats directory.

PoC

Prerequisites:
- Valid authenticated session cookie (cookie.txt)
- Valid CSRF token ($TOKEN)

Read sensitive file (secrets.json):

curl -b cookie.txt -H "x-csrf-token: $TOKEN" -H "content-type: application/json" \
  -d '{"avatar_url":"..","is_group":false,"file":"secrets.json","format":"jsonl","exportfilename":"x"}' \
  http://TARGET:8000/api/chats/export

Delete sensitive file (settings.json):

curl -b cookie.txt -H "x-csrf-token: $TOKEN" -H "content-type: application/json" \
  -d '{"avatar_url":"..","chatfile":"settings.json"}' \
  http://TARGET:8000/api/chats/delete

Impact

• Confidentiality: exposed per-user secrets and config data.
• Integrity/Availability: attacker can delete critical per-user files and break account operation.
• Risk is significant in multi-user or remotely reachable deployments.

Resolution

The issue was addressed in version 1.17.0