GHSA-4mgv-366x-qxvx: 
PHP vulnerability analysis and mitigation

Overview of all XSS Reports

Multiple stored XSS vulnerabilities were found in Craft CMS. They were split into 4 reports as follows:

Summary

Affected Sources

Proof of Concept

Required Permissions (Attacker)

• Admin access
• allowAdminChanges is enabled in production, which is against our security recommendations.

Bugs 1-3: Section, Volume, User Group Names

1. Log in as admin.
2. Inject payload in one of these:
   • Settings -> Sections -> Create/edit section -> Name
   • Settings -> Assets -> Volumes -> Create/edit volume -> Name
   • Settings -> Users -> User Groups -> Create/edit group -> Name
3. Set Name to:

<img src=x onerror="alert('XSS')">

4. Save.
5. Go to Settings -> Fields -> Create new field.
6. To trigger the XSS payload: Set Field Type to "Entries" (for Sections), "Assets" (for Volumes), or "Users" (for User Groups). The alert fires when the Sources checkbox list renders. Note: User Group Name also reflects on User permissions page under User Groups section (/admin/users/{id}/permissions).

Bug 4: Global Set Name

1. Go to Settings -> Globals (/admin/settings/globals).
2. Create/edit a Global Set, set Name to payload.
3. Save.
4. Go to Users -> Edit any user -> Permissions tab (/admin/users/{id}/permissions).
5. Alert fires because our payload got rendered in the "Global Sets" permissions section without encoding/sanitization.

Bug 5: Generated Fields Name

1. Go to Settings -> Assets -> Volumes -> Create/Edit a volume.
2. Scroll to Generated Fields section.
3. Add a field, set Name to payload:

<img src=x onerror="alert('XSS')">

4. Save & Notice the alert. The payload renders in the Card Attributes checkbox list below it.

Bug 6: Checkboxes/Radio Buttons Option Label

1. Go to Settings -> Fields (/admin/settings/fields).
2. Create new field, set Field Type to "Checkboxes" or "Radio Buttons".
3. In Field Options, add an option with Label set to payload.
4. Save the field.
5. Go to Settings -> Users -> User Profile Fields (/admin/settings/users/fields).
6. Add the created field to the layout and save.
7. Alert fires on any user profile page (/admin/users/{id}).

Bug 7: Custom Sources Label

1. Go to Users (/admin/users).
2. Click the three dots icon -> Customize Sources.
3. Create a new custom source, set Label to payload.
4. Save.
5. Go to Settings -> Fields -> Create new field.
6. Set Field Type to "Users".
7. Alert fires in the Sources checkbox list.

Resources

https://github.com/craftcms/cms/commit/943152d2246b36f12adf161a03b8695b773d9276 https://github.com/craftcms/cms/commit/67780a778c6ec04e68e64a0b1177c168306144a2