CVE-2021-28115Public exploitNetwork attack vector

Stored XSS via unescaped edited feedback comment

Published Mar 9, 2021 · Updated Aug 3, 2024

Stored XSS in OUGC Feedback before 1.8.23 for MyBB allows remote attackers to execute script in a user's browser through an edited comment. During feedback editing, Upload/feedback.php copies the stored comment into $mybb->input['comment'] and renders the ougcfeedback_form_comment template without first applying HTML escaping. Execution requires a user to open the affected edit view and runs in that user's web context, enabling access to or modification of data exposed to that session.

CVSS severity6.1
Medium
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in OUGC Feedback before 1.8.23 for MyBB allows remote attackers to execute script in a user's browser through an edited comment. During feedback editing, Upload/feedback.php copies the stored comment into $mybb->input['comment'] and renders the ougcfeedback_form_comment template without first applying HTML escaping. Execution requires a user to open the affected edit view and runs in that user's web context, enabling access to or modification of data exposed to that session.

The record

CVE
CVE-2021-28115
Published
Mar 9, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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