Formstone Vulnerable to Reflected XSS

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-2020-26768: 1.28% estimated exploitation activity in the next 30 days; percentile 70.00 (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.

Formstone <=1.4.16 is vulnerable to a Reflected Cross-Site Scripting (XSS) vulnerability caused by improper validation of user supplied input in the upload-target.php and upload-chunked.php files. A remote attacker could exploit this vulnerability using a specially crafted URL to execute a script in a victim's Web browser within the security context of the hosting Web site once the URL is clicked or visited. An attacker could use this vulnerability to steal the victim's cookie-based authentication credentials, force malware execution, user redirection and others.

Published by the source

24 May 2022, 17:38 UTC

Last modified by the source

1 Apr 2024, 22:27 UTC

Source last checked

26 Oct 2026, 12:30 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-wc29-h54q-q8qx

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-wc29-h54q-q8qx

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2020-26768

Advisory: Formstone Vulnerable to Reflected XSS
IDs: CVE-2020-26768, GHSA-wc29-h54q-q8qx
Record: https://patchnext.com/advisories/cve-2020-26768 (revision 2, source checked 26 Oct 2026, 12:30 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: formstone 1.4.17. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm formstone: affected <= 1.4.16; fixed in 1.4.17

## Suggested inspection (read-only)
- `npm ls formstone --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## 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 formstone.
- 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-wc29-h54q-q8qx (OSV record GHSA-wc29-h54q-q8qx lists affected ranges: npm formstone >=0 <1.4.17 (fixed))
- Verified: https://github.com/advisories/GHSA-wc29-h54q-q8qx (GitHub-reviewed advisory GHSA-wc29-h54q-q8qx lists affected ranges: npm formstone >=0 <=1.4.16)

Commands are suggestions: review each one before running it.