changedetection.io Vulnerable to Reflected XSS in RSS Single Watch Error Response

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-27645: 0.50% estimated exploitation activity in the next 30 days; percentile 42.56 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Three security vulnerabilities were identified in changedetection.io through source code review and live validation against a locally deployed Docker instance. All vulnerabilities were confirmed exploitable on the latest version (0.53.6) it was additionally validated at scale against 500 internet-facing instances discovered via FOFA search engine, producing 5K+ confirmed detections using a custom Nuclei template, demonstrating widespread real-world impact. The RSS single-watch endpoint reflects the UUID path parameter directly in the HTTP response body without HTML escaping. Since Flask returns text/html by default for plain string responses, the browser parses and executes injected JavaScript. Details File: changedetectionio/blueprint/rss/singlewatch.py (lines ~45 and ~50) The UUID parameter from the URL path is interpolated into the response body using an f-string with no escaping: Line ~45 Line ~50 Attack Vector The attack requires a valid RSS access token, which is a…

Published by the source

25 Feb 2026, 19:07 UTC

Last modified by the source

13 Jul 2026, 07:26 UTC

Source last checked

26 Oct 2026, 13:36 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-mw8m-398g-h89w

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-mw8m-398g-h89w

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# Patch Next advisory brief: CVE-2026-27645

Advisory: changedetection.io Vulnerable to Reflected XSS in RSS Single Watch Error Response
IDs: CVE-2026-27645, GHSA-mw8m-398g-h89w
Record: https://patchnext.com/advisories/cve-2026-27645 (revision 2, source checked 26 Oct 2026, 13:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: changedetection-io 0.53.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI changedetection-io: affected <= 0.53.6; fixed in 0.53.7

## Suggested inspection (read-only)
- `python -m pip show changedetection-io`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on changedetection-io.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-mw8m-398g-h89w (OSV record GHSA-mw8m-398g-h89w lists affected ranges: PyPI changedetection-io >=0 <0.53.7 (fixed))
- Verified: https://github.com/advisories/GHSA-mw8m-398g-h89w (GitHub-reviewed advisory GHSA-mw8m-398g-h89w lists affected ranges: PyPI changedetection-io >=0 <=0.53.6)

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