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Craft CMS: DOM XSS via GitHub issue title in CraftSupport widget

High severity GitHub Reviewed Published Jun 16, 2026 in craftcms/cms • Updated Jul 6, 2026

Package

composer craftcms/cms (Composer)

Affected versions

>= 5.0.0-RC1, < 5.9.22
>= 4.0.0-RC1, < 4.17.15

Patched versions

5.9.23
4.17.16

Description

Summary

An attacker with only a GitHub account can plant a JavaScript payload in a craftcms/cms issue title. When a Craft admin uses the CraftSupport widget’s "Give feedback" screen and types a search term that returns the poisoned issue, the payload executes in the admin’s control panel session.

No control panel account or elevated privileges are required on the attacker’s side.

Preconditions

  • Attacker has a GitHub account (no control panel access needed).
  • Victim is an administrator, and you have the CraftSupport widget on the dashboard.
  • Victim uses the "Give feedback" screen and types a search term that returns the poisoned issue.

Root cause

CraftSupportWidget.js lines 382-392:

$('<a>', {
  href: this.getSearchResultUrl(results[i]),
  target: '_blank',
  html:
    '<span class="status ' +
    this.getSearchResultStatus(results[i]) +
    '"></span>' +
    this.getSearchResultText(results[i]),
})

FeedbackScreen.getSearchResultText (line 669-671) returns result.title verbatim from the GitHub API response. The jQuery html: option sets the element’s innerHTML, so a title containing <img src=x onerror=...> executes immediately on render.

The GitHub API returns issue titles as raw JSON strings with no HTML encoding. The widget makes this request directly from the browser, without a Craft proxy or any sanitization step.

HelpScreen (Stack Exchange) is not affected because the Stack Exchange API HTML-encodes titles before returning them.

Steps to reproduce

Plant (attacker, GitHub account only):

  1. Open https://github.com/craftcms/cms/issues/new.
  2. Set the title to a string combining a plausible search term and the payload, e.g.:
<img src=x onerror=alert(document.domain)> cannot upload files
  1. Submit the issue.

Trigger (victim, Craft admin):

  1. Open the Craft control panel dashboard.
  2. Open the CraftSupport widget, click "Give feedback".
  3. Type cannot upload files in the search box.
  4. alert(document.domain) fires in the admin's session.

Impact

XSS in the admin control panel session. The payload has access to Craft.csrfTokenName and Craft.csrfTokenValue and can send same-origin action requests as the admin without any further interaction.

Mitigating factors

  • Victim must actively use the "Give feedback" search screen.
  • Attacker must predict or social-engineer a search term the admin will type, or use a broad term likely to match.
  • Widget is only available to admins.

Resources

craftcms/cms@6bbb660

References

@angrybrad angrybrad published to craftcms/cms Jun 16, 2026
Published by the National Vulnerability Database Jul 1, 2026
Published to the GitHub Advisory Database Jul 6, 2026
Reviewed Jul 6, 2026
Last updated Jul 6, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements Present
Privileges Required None
User interaction Active
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(23rd percentile)

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Learn more on MITRE.

CVE ID

CVE-2026-55790

GHSA ID

GHSA-24x4-j6x9-rfw5

Source code

Credits

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