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Critical, CVSS 9.3amended

Grav: detectXss() misses an event-handler attribute after an unpaired quote in an unquoted attribute value, giving stored XSS

CVE-2026-75828GHSA-vfmf-q6x9-cw96

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (getgrav/grav 2.0.15), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
9.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N · score source
EPSS
  • CVE-2026-75828: 0.39% estimated exploitation activity in the next 30 days; percentile 33.07 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Affected versions and vulnerable location - Confirmed on grav core at 78ebfc1 (tag 2.0.13). - Detector: system/src/Grav/Common/Security.php:290, the onevents regex, run via patternMatches() (:315-330). - The onevents pattern at HEAD: #<(?:"[^"]"|'[^']'|[^"'])?(?:[\s\x00-\x20"'/]|"[^"]"|'[^']')on\s[a-z]+\s=#iu - Sole save-time guard for non-super content: Validation::checkSafety() (system/src/Grav/Common/Data/Validation.php:160 scalars, :165 arrays), invoked per field from BlueprintSchema::validate - Validation::checkSafety (system/src/Grav/Common/Data/BlueprintSchema.php:248). security.xsswhitelist: [admin.super] exempts only super-admins (Validation.php:148). Root cause (distinct from GHSA-269c) GHSA-269c hardened the tag-body scan to be quote-aware so a inside a paired quoted attribute value is treated as data, not a tag close. That same quote-awareness opened a new gap: the regex treats ANY " or ' as a string delimiter, but HTML only enters a quoted-value state when a quote…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-vfmf-q6x9-cw96

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-vfmf-q6x9-cw96

Agent brief

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# Patch Next advisory brief: CVE-2026-75828

Advisory: Grav: detectXss() misses an event-handler attribute after an unpaired quote in an unquoted attribute value, giving stored XSS
IDs: CVE-2026-75828, GHSA-vfmf-q6x9-cw96
Record: https://patchnext.com/advisories/cve-2026-75828 (revision 3, source checked 26 Oct 2026, 14:53 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: getgrav/grav 2.0.15. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist getgrav/grav: affected <= 2.0.14; fixed in 2.0.15

## Suggested inspection (read-only)
- Packagist getgrav/grav: check the installed version with your package manager.

## 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 getgrav/grav.
- 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-vfmf-q6x9-cw96 (OSV record GHSA-vfmf-q6x9-cw96 lists affected ranges: Packagist getgrav/grav >=0 <2.0.15 (fixed))
- Verified: https://github.com/advisories/GHSA-vfmf-q6x9-cw96 (GitHub-reviewed advisory GHSA-vfmf-q6x9-cw96 lists affected ranges: Packagist getgrav/grav >=0 <=2.0.14)

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