CVE-2026-33209Public exploitNetwork attack vector

JavaScript execution via failed return_to decryption

Published Mar 20, 2026 · Updated Mar 20, 2026

Reflected XSS in Avo before 3.30.3 allows remote attackers to execute JavaScript through a crafted return_to query parameter. ApplicationHelper#d returned the original value when return_to decryption failed, allowing a javascript URL to become a generated Go back link. A user must open the crafted URL and click the generated navigation link; access depends on whether the host Rails app exposes Avo without authentication.

CVSS severity5.3
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in Avo before 3.30.3 allows remote attackers to execute JavaScript through a crafted return_to query parameter. ApplicationHelper#d returned the original value when return_to decryption failed, allowing a javascript URL to become a generated Go back link. A user must open the crafted URL and click the generated navigation link; access depends on whether the host Rails app exposes Avo without authentication.

The record

CVE
CVE-2026-33209
Published
Mar 20, 2026
Updated
Mar 20, 2026
Vendor
Avo
Product
Avo
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 20, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.30.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Avo · Avoversion=< 3.30.3

Published CVSS scores

5.3GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA: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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

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

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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