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NVD / CVE Program· CNA WPScan

CVE-2023-6621: Post SMTP < 2.8.7 - Reflected Cross-Site Scripting

MediumCVSS 6.1 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 24/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.40% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: Unknown POST SMTP 2.8.7.

Low priority for now. Upgrade to Unknown POST SMTP 2.8.7 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

The POST SMTP WordPress plugin before 2.8.7 does not sanitise and escape the msg parameter before outputting it back in the page, leading to a Reflected Cross-Site Scripting which could be used against high privilege users such as admin.

Published
Jan 3, 2024
Updated
Jun 17, 2026
EPSS
0.4% · 34th percentile

Report tools

JSON

Action score

24

Monitor

Low priority for now.

CVSS
24 / 40 · 6.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Is Post SMTP – Complete Email Delivery and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App on your site?

WP Lens reads your site's plugin, theme and WordPress versions from the outside and matches them to known vulnerabilities. Works without an account.

Follow CVE-2023-6621

Is Post SMTP – Complete Email Delivery and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App on your site?

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
wpexpertspost smtp

Versions reported by the vendor

Affected version ranges reported by the assigning authority (WPScan). Independent of NVD's CPE analysis and usually ahead of it.

  • Unknown POST SMTP

    • before 2.8.7affected · semver

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • wpexperts post smtpbefore 2.8.7

Same product

wpexperts: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-6875POST SMTP Mailer – Email log, Delivery Failure Notifications and Best Mail SMTP for WordPress <= 2.8.7 - Authorization Bypass via type connect-app API
    66This week
  • CVE-2023-52233WordPress POST SMTP Mailer plugin <= 2.8.6 - Broken Access Control on API vulnerability
    39Monitor
  • CVE-2025-22800WordPress Post SMTP plugin <= 2.9.11 - Broken Access Control vulnerability
    35Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2023-6629Jan 3, 2024 · POST SMTP Mailer <= 2.8.6 - Reflected Cross-Site Scripting via msg
    24Monitor
  • ← EarlierCVE-2023-7027Jan 3, 2024 · POST SMTP Mailer – Email log, Delivery Failure Notifications and Best Mail SMTP for WordPress <= 2.8.7 - Unauthenticated Stored Cross-Site Scripting via device
    21Monitor
  • Later →CVE-2023-6620Jan 15, 2024 · Post SMTP < 2.8.7 - Admin+ SQL Injection
    32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Unknown POST SMTP2.8.7Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2023-66290 days apartPOST SMTP Mailer <= 2.8.6 - Reflected Cross-Site Scripting via msg
    24Monitor
  • CVE-2023-595837 days apartPOST SMTP Mailer < 2.7.1 - Unauthenticated Cross-site Scripting
    24Monitor
  • CVE-2024-2912876 days apartWordPress POST SMTP Mailer plugin <= 2.8.6 - Reflected Cross Site Scripting (XSS) vulnerability
    24Monitor
  • CVE-2023-3082175 days apartPost SMTP <= 2.5.7 - Unauthenticated Stored Cross-Site Scripting via Email
    24Monitor
  • CVE-2025-0521412 days apartPost SMTP <= 3.0.2 - Unauthenticated Stored Cross-Site Scripting
    24Monitor
  • CVE-2023-70270 days apartPOST SMTP Mailer – Email log, Delivery Failure Notifications and Best Mail SMTP for WordPress <= 2.8.7 - Unauthenticated Stored Cross-Site Scripting via device
    21Monitor

Not on record for this CVE: EPSS history · patch commit or PR link · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

nvd-primary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

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All records