GHSA-9695-8fr9-hw5q

Source

https://github.com/advisories/GHSA-9695-8fr9-hw5q

Import Source

https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-9695-8fr9-hw5q/GHSA-9695-8fr9-hw5q.json

JSON Data

https://api.osv.dev/v1/vulns/GHSA-9695-8fr9-hw5q

Aliases

CVE-2026-42612

Published

2026-05-05T21:27:15Z

Modified

2026-09-10T03:51:05Z

Severity

8.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N CVSS Calculator

Summary

Grav Vulnerable to Publisher-Level Stored XSS via Unquoted Event Attributes

Details

Summary

A stored Cross-Site Scripting (XSS) vulnerability in getgrav/grav allows publisher-level accounts to execute arbitrary JavaScript. The issue arises from a blacklist bypass in the detectXss() function when handling unquoted HTML event attributes.

Details

The detectXss() function relies on a blacklist pattern to filter malicious attributes. The specific regex pattern used to match on* events is flawed:

'on_events' => '#(<[^>]+[a-z\x00-\x20\"\'\/])(on[a-z]+|xmlns)\s*=[\s|\'\"].*[\s|\'\"]>#iUu'

This pattern fails to properly identify on* event handlers that are constructed without quotation marks. This allows an attacker to completely bypass the filter. Note: It is highly recommended to replace this blacklist approach with a robust, established HTML sanitization library.

PoC

An attacker with publisher-level access can reproduce this by injecting the following payload into any vulnerable content field:

<img src=x onerror=eval(atob(/YWxlcnQoZG9jdW1lbnQuY29va2llKQ/.source))>

Execution Details: The onerror event is written without quotes to bypass the regex. Because unquoted attributes are restricted in their character usage (e.g., the = symbol cannot be used easily), the payload leverages atob() and regex .source to decode the base64 string YWxlcnQoZG9jdW1lbnQuY29va2llKQ (which translates to alert(document.cookie)). The atob() function conveniently auto-completes the necessary = padding for the base64 string.

Impact

Vulnerability Type: Stored Cross-Site Scripting (XSS)
Impacted Parties: Any user (including administrators) who views the compromised content published by the attacker.
Consequences: Attackers can execute malicious scripts in a victim's browser, leading to session hijacking (cookie theft), unauthorized actions.

Maintainer note — fix applied (2026-04-24)

Fixed in Grav core on the 2.0 branch: commit 5a12f9be8 — will ship in 2.0.0-beta.2.

What changed: the on_events regex in Security::detectXss() no longer requires quotes or whitespace around =. The previous form:

'on_events' => '#(<[^>]+[\s\x00-\x20\"\'\/])(on\s*[a-z]+|xmlns)\s*=[\s|\'\"].*[\s|\'\"]>#iUu'

required [\s|'"] immediately after the =, so <img src=x onerror=alert(1)> slid past. The new regex drops the value-matching tail entirely and just flags the presence of an on*= attribute anywhere inside a tag:

'on_events' => '#<[^>]*?[\s\x00-\x20\"\'\/](on\s*[a-z]+|xmlns)\s*=#iu'

Detecting the attribute name + = is enough for a tripwire — the trade-off is occasional false positives on legitimate attribute values containing on*= substrings, which the maintainer can hand-approve.

This same regex bypass was the detection-layer half of GHSA-c2q3-p4jr-c55f and GHSA-w8cg-7jcj-4vv2; the fix here knocks both down.

Files:

system/src/Grav/Common/Security.php.
tests/unit/Grav/Common/Security/DetectXssTest.php — 18 cases: unquoted PoCs, quoted-form regression, safe-content negatives.

Database specific

{
    "cwe_ids":  [
        "CWE-79"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-05-05T21:27:15Z",
    "nvd_published_at":  "2026-05-11T16:17:34Z",
    "severity":  "HIGH"
}

References

Affected packages

Packagist / getgrav/grav

Package

Name: getgrav/grav
Purl: pkg:composer/getgrav/grav

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Fixed

2.0.0-beta.2

Affected versions

0.*

0.8.0

0.9.0

0.9.1

0.9.2

0.9.3

0.9.4

0.9.5

0.9.6

0.9.7

0.9.8

0.9.9

0.9.10

0.9.11

0.9.12

0.9.13

0.9.14

0.9.15

0.9.16

0.9.17

0.9.18

0.9.19

0.9.20

0.9.21

0.9.22

0.9.23

0.9.24

0.9.25

0.9.26

0.9.27

0.9.28

0.9.29

0.9.30

0.9.31

0.9.32

0.9.33

0.9.34

0.9.35

0.9.36

0.9.37

0.9.38

0.9.39

0.9.40

0.9.41

0.9.42

0.9.43

0.9.44

0.9.45

1.*

1.0.0-rc.1

1.0.0-rc.2

1.0.0-rc.3

1.0.0-rc.4

1.0.0-rc.5

1.0.0-rc.6

1.0.0

1.0.1

1.0.2

1.0.3

1.0.4

1.0.5

1.0.6

1.0.7

1.0.8

1.0.9

1.0.10

1.1.0-beta.1

1.1.0-beta.2

1.1.0-beta.3

1.1.0-beta.4

1.1.0-beta.5

1.1.0-rc.1

1.1.0-rc.2

1.1.0-rc.3

1.1.0

1.1.1

1.1.2

1.1.3

1.1.4

1.1.5

1.1.6

1.1.7

1.1.8

1.1.9-rc.1

1.1.9-rc.2

1.1.9-rc.3

1.1.9

1.1.10

1.1.11

1.1.12

1.1.13

1.1.14

1.1.15

1.1.16

1.1.17

1.2.0-rc.1

1.2.0-rc.2

1.2.0-rc.3

1.2.0

1.2.1

1.2.2

1.2.3

1.2.4

1.3.0-rc.1

1.3.0-rc.2

1.3.0-rc.3

1.3.0-rc.4

1.3.0-rc.5

1.3.0

1.3.1

1.3.2

1.3.3

1.3.4

1.3.5

1.3.6

1.3.7

1.3.8

1.3.9

1.3.10

1.4.0-beta.1

1.4.0-beta.2

1.4.0-beta.3

1.4.0-rc.1

1.4.0-rc.2

1.4.0

1.4.1

1.4.2

1.4.3

1.4.4

1.4.5

1.4.6

1.4.7

1.4.8

1.5.0-beta.1

1.5.0-beta.2

1.5.0-rc.1

1.5.0

1.5.1

1.5.2

1.5.3

1.5.4

1.5.5

1.5.6

1.5.7

1.5.8

1.5.9

1.5.10

1.6.0-beta.1

1.6.0-beta.2

1.6.0-beta.3

1.6.0-beta.4

1.6.0-beta.5

1.6.0-beta.6

1.6.0-beta.7

1.6.0-beta.8

1.6.0-rc.1

1.6.0-rc.2

1.6.0-rc.3

1.6.0-rc.4

1.6.0

1.6.1

1.6.2

1.6.3

1.6.4

1.6.5

1.6.6

1.6.7

1.6.8

1.6.9

1.6.10

1.6.11

1.6.12

1.6.13

1.6.14

1.6.15

1.6.16

1.6.17

1.6.18

1.6.19

1.6.20

1.6.21

1.6.22

1.6.23

1.6.24

1.6.25

1.6.26

1.6.27

1.6.28

1.6.29

1.6.30

1.6.31

1.7.0-beta.1

1.7.0-beta.2

1.7.0-beta.3

1.7.0-beta.4

1.7.0-beta.5

1.7.0-beta.6

1.7.0-beta.7

1.7.0-beta.8

1.7.0-beta.9

1.7.0-beta.10

1.7.0-rc.1

1.7.0-rc.2

1.7.0-rc.3

1.7.0-rc.4

1.7.0-rc.5

1.7.0-rc.6

1.7.0-rc.7

1.7.0-rc.8

1.7.0-rc.9

1.7.0-rc.10

1.7.0-rc.11

1.7.0-rc.12

1.7.0-rc.13

1.7.0-rc.14

1.7.0-rc.15

1.7.0-rc.16

1.7.0-rc.17

1.7.0-rc.18

1.7.0-rc.19

1.7.0-rc.20

1.7.0

1.7.1

1.7.3

1.7.4

1.7.5

1.7.6

1.7.7

1.7.8

1.7.9

1.7.10

1.7.12

1.7.13

1.7.14

1.7.15

1.7.16

1.7.17

1.7.18

1.7.19

1.7.20

1.7.21

1.7.22

1.7.23

1.7.24

1.7.25

1.7.26

1.7.26.1

1.7.27

1.7.27.1

1.7.28

1.7.29

1.7.29.1

1.7.30

1.7.31

1.7.32

1.7.33

1.7.34

1.7.35

1.7.36

1.7.37

1.7.37.1

1.7.38

1.7.39

1.7.39.1

1.7.39.2

1.7.39.3

1.7.39.4

1.7.40

1.7.41

1.7.41.1

1.7.41.2

1.7.42

1.7.42.1

1.7.42.2

1.7.42.3

1.7.43

1.7.44

1.7.45

1.7.46

1.7.47

1.7.48

1.7.49

1.7.49.1

1.7.49.2

1.7.49.3

1.7.49.4

1.7.49.5

1.7.51

1.7.52

1.7.53

1.7.53.1

1.7.53.2

1.7.53.3

1.8.0-beta.1

1.8.0-beta.2

1.8.0-beta.3

1.8.0-beta.4

1.8.0-beta.5

1.8.0-beta.6

1.8.0-beta.7

1.8.0-beta.8

1.8.0-beta.9

1.8.0-beta.10

1.8.0-beta.11

1.8.0-beta.12

1.8.0-beta.13

1.8.0-beta.14

1.8.0-beta.15

1.8.0-beta.16

1.8.0-beta.17

1.8.0-beta.18

1.8.0-beta.19

1.8.0-beta.20

1.8.0-beta.21

1.8.0-beta.22

1.8.0-beta.23

1.8.0-beta.24

1.8.0-beta.25

1.8.0-beta.26

1.8.0-beta.27

1.8.0-beta.28

1.8.0-beta.29

2.*

2.0.0-beta.1

Database specific

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-9695-8fr9-hw5q/GHSA-9695-8fr9-hw5q.json"