Stored Cross-Site Scripting in AppFlowy Cloud by AppFlowy
CVE-2026-127203

5.1MEDIUM

Key Information:

Vendor

Appflowy-io

Status
Appflowy-cloud
Vendor
CVE Published:
12 November 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-127203?

AppFlowy Cloud versions up to 0.9.64 are vulnerable to a stored cross-site scripting (XSS) issue. This vulnerability allows authenticated users to upload blobs with non-validated Content-Type headers. Once uploaded, these blobs can be served as active HTML content through unsecured retrieval endpoints. As a result, any visitor accessing the URL can be subjected to persistent script execution, compromising user data and web security by injecting malicious scripts. Awareness of this vulnerability is crucial for maintaining secure application environments.

Affected Version(s)

AppFlowy-Cloud 0 <= 0.9.64

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-127203 - Proof of Concept

References

https://gist.github.com/mtholmquist/9b9683104fc3b5d78a488...
technical-descriptionexploit
https://www.vulncheck.com/advisories/appflowy-cloud-store...
third-party-advisory

CVSS V4

Score:
5.1
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Michael Holmquist (@mtholmquist), Hasp Labs.
.