Subscribe to Comments: Email header injection through sender settings
The Subscribe to Comments WordPress plugin from 2.3 up to, but not including, 2.3.3 does not sanitise newline characters from a notification sender-name setting before using it in e-mail headers, allowing users with Author-level access and above to inject arbitrary e-mail headers, such as a hidden Bcc, and to spoof the sender. The export does not name an endpoint, action, parameter or function beyond the operation described. The CNA narrative names Author access or higher, while the accompanying CVSS vector rates required privileges as high; this source discrepancy is retained rather than substituting a different WordPress role. The completed CNA record identifies 2.3.3 as fixed.
- Component
- Subscribe to Comments
- Plugin slug
subscribe-to-comments- Affected
- 2.3 to < 2.3.3
- Safe version
2.3.3- Published
- Oct 19, 2026
This CVE was published Oct 19, 2026 and is one of 7 known issues for this plugin.
Update, patch or deactivate.
Update Subscribe to Comments to 2.3.3 or a later supported release. The completed CNA record identifies this fixed boundary. Reject carriage returns and newlines in sender-name values before constructing mail headers, and restrict changes to authorized administrators.
A safe version is available, so updating to that version or later is the preferred remediation. If an immediate update is not practical, consider a targeted application patch or temporarily restricting the affected functionality.
Deactivate only when warranted by your risk profile, or when advised by your hosting provider in the limited circumstances where the vulnerability cannot otherwise be mitigated. If you’re unsure which action is appropriate, contact Fused or your hosting provider for guidance.
Technical description
The Subscribe to Comments WordPress plugin before 2.3.3 does not sanitise newline characters from a notification sender-name setting before using it in e-mail headers, allowing users with Author-level access and above to inject arbitrary e-mail headers, such as a hidden Bcc, and to spoof the sender.
CVE / CNA vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N