Cross Site Scripting (XSS) in MyBB v1.8.20 allows remote attackers to inject arbitrary web script or HTML via the "Title" field found in the "Add New Forum" page by doing an authenticated POST HTTP request to '/Upload/admin/index.php?module=forum-management&action=add'.
CVSS v4.0 Metrics
Exploitability
Attack VectorNetwork
ComplexityLow
RequirementsPresent
PrivilegesLow
User InteractionActive
Threat
Exploit MaturityUnreported
Vulnerable System
ConfidentialityLow
IntegrityLow
AvailabilityNone
Subsequent System
ConfidentialityNone
IntegrityNone
AvailabilityNone
Supplemental
SafetyNegligible
AutomatableYes
RecoveryAutomatic
Value DensityConcentrated
UrgencyMedium
Change Log
| Date | Source | Changes | Score |
|---|
| 2026-07-21 | nvd | AV: P→N, AC: H→L, PR: H→L, VC: N→L, VI: N→L | 0.0 → 0.4 |
| 2026-07-21 | cve.org | initial, patch: Unavailable | 0.0 |
Affected Software
| Vendor | Product | Version |
|---|
| mybb | mybb | 1.8.20 |
Published: 2021-08-31
