CVE-2023-37658Public exploitNetwork attack vector

Stored XSS via extension-blind image upload

Published Jul 11, 2023 · Updated Nov 8, 2024

Stored XSS in fast-poster 2.15.0 allows remote authenticated users to execute JavaScript in another user's browser via an uploaded file. ApiUploadHandler.post in server/fast.py validates uploaded image bytes but does not restrict the filename suffix, so an image and HTML polyglot is stored and served as HTML. Exploitation requires authenticated upload access and a victim to open the stored file, exposing browser-accessible data and actions in the application's origin.

CVSS severity5.4
Medium
EPSS probability0.38%
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 fast-poster 2.15.0 allows remote authenticated users to execute JavaScript in another user's browser via an uploaded file. ApiUploadHandler.post in server/fast.py validates uploaded image bytes but does not restrict the filename suffix, so an image and HTML polyglot is stored and served as HTML. Exploitation requires authenticated upload access and a victim to open the stored file, exposing browser-accessible data and actions in the application's origin.

The record

CVE
CVE-2023-37658
Published
Jul 11, 2023
Updated
Nov 8, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 11, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

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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