CVE-2026-25156Network attack vector

Stored XSS via unsafe inline document delivery

Published Jan 30, 2026 · Updated Jan 30, 2026

Stored XSS in HotCRP 3.2 allows remote authenticated users to execute script in another user's browser through an uploaded document. The /doc/ handler defaulted the Downloader attachment flag to false, so uploaded HTML or SVG was served inline rather than limiting inline rendering to whitelisted MIME types. A viewer must open the document link; the script then runs with that viewer's HotCRP credentials and can make arbitrary HotCRP API calls.

CVSS severity7.3
High
EPSS probability0.24%
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 HotCRP 3.2 allows remote authenticated users to execute script in another user's browser through an uploaded document. The /doc/ handler defaulted the Downloader attachment flag to false, so uploaded HTML or SVG was served inline rather than limiting inline rendering to whitelisted MIME types. A viewer must open the document link; the script then runs with that viewer's HotCRP credentials and can make arbitrary HotCRP API calls.

The record

CVE
CVE-2026-25156
Published
Jan 30, 2026
Updated
Jan 30, 2026
Vendor
Eddie Kohler
Product
HotCRP
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 30, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 30, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion== 3.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Eddie Kohler · HotCRPversion== 3.2

Published CVSS scores

6.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N
7.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1204.001Malicious Link

Public exploit references

No public exploit references are available in this record.

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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