---
id: "CVE-2026-127203"
page: "https://infrastack.ai/live/CVE-2026-127203"
kind: "vulnerability"
aliases: ["CVE-2026-127203"]
title: "AppFlowy Cloud: uploaded HTML files run scripts in visitors' browsers"
severity: "medium"
cvss: 5.4
epss: null
exploited: false
status: "open"
category: "other"
products: [{"name": "AppFlowy Cloud", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["appflowy-cloud", "other", "self-hosted"]
not_affected_if: ["newer-version", "no-file-uploads"]
published_at: "2026-11-12T17:17:43+00:00"
first_seen_at: "2026-11-12T17:39:39+00:00"
updated_at: "2026-11-12T17:40:06+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-127203", "first_seen_at": "2026-11-12T17:39:39+00:00"}]
exploit_sources: []
---

# AppFlowy Cloud: uploaded HTML files run scripts in visitors' browsers

Link for people: https://infrastack.ai/live/CVE-2026-127203 (this .md is for agents)

AppFlowy Cloud through 0.9.64 serves uploaded files with an attacker-chosen content type and no download header, so an uploaded HTML or SVG file runs as a page on the AppFlowy domain. An attacker who is a workspace member can make any visitor who opens the link run scripts in their session, and the response is cached for a year.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:AppFlowy Cloud affected range not listed fixed no fixed version listed

## How to check

- Check the AppFlowy Cloud version with the deployed image tag or release (`0.9.64` or earlier is affected per the sources)
- Look for the `put_blob_handler` and `get_blob_handler` routes in the deployed build's source if you build from source

## Timeline

- 2026-11-12T17:39:39+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-127203

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/appflowy-cloud-stored-xss-via-blob-upload-content-type

## From the sources

AppFlowy Cloud through 0.9.64 contains a stored cross-site scripting vulnerability that allows authenticated workspace members to upload blobs with unvalidated Content-Type values that are later served inline without a Content-Disposition header or authentication on the retrieval route. Attackers can upload a text/html or image/svg+xml blob via put_blob_handler, which is then rendered as an active same-origin document through the unauthenticated get_blob_handler endpoint and cached immutably for one year, enabling persistent script execution against any visitor who accesses the URL.

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