GHSA-v5mq-3xhg-98m9

Suggest an improvement
Source
https://github.com/advisories/GHSA-v5mq-3xhg-98m9
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-v5mq-3xhg-98m9/GHSA-v5mq-3xhg-98m9.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-v5mq-3xhg-98m9
Aliases
Published
2026-10-15T20:16:18Z
Modified
2026-10-15T20:30:08Z
Severity
  • 6.1 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N CVSS Calculator
Summary
unstructured: Stored XSS via unescaped HTML generation
Details

Summary

When unstructured parses an untrusted document and outputs the result as HTML, malicious markup contained in the document (e.g. <img src=x onerror=...>) is left in the output HTML without escaping. When that output is displayed in a browser, the script embedded in the document executes in the viewer's browser.

Details

partition_html(html_parser_version="v2") (and the VLM partitioner) preserve the input document's element tags, attributes, and text into metadata.text_as_html, and elements_to_html() outputs that as an HTML document.

The function that builds HTML on this path, to_html() in unstructured/documents/ontology.py, performs no escaping at all. As a result, event handlers such as onerror / onmouseover / onload originating from the input document are left in the output HTML as-is (literal <script> tags are stripped by the parser, but attribute-based vectors and javascript: URLs are not). In addition, link URLs are not scheme-filtered, so <a href="javascript:..."> is also emitted.

Relevant source: documents/ontology.py (to_html, _construct_attribute_string, _generate_final_html); partition/html/transformations.py (text_as_html = ontology_element.to_html()); partition/html/convert.py (elements_to_html).

PoC

Environment: downloads.unstructured.io/unstructured-io/unstructured:latest, unstructured 0.23.3.

from unstructured.partition.html import partition_html
from unstructured.partition.html.convert import elements_to_html

malicious = ('<body class="Document">'
             '<p class="Paragraph" onmouseover="alert(1)">hello'
             '<img src=x onerror="alert(document.domain)"></p>'
             '<a class="Hyperlink" href="javascript:alert(document.cookie)">click me</a>'
             '</body>')
els = partition_html(text=malicious, html_parser_version="v2")
open("xss_output.html", "w").write(elements_to_html(list(els), no_group_by_page=True))

elements_to_html() output body — the unescaped vectors survive:

<p class="NarrativeText" id="..." onmouseover="alert(1)">
  <p class="Paragraph">hello</p>
  <img class="Image" onerror="alert(document.domain)" src="x"/>
</p>
<a class="UncategorizedText" href="javascript:alert(document.cookie)" id="...">click me</a>

Opening xss_output.html in a browser fires alert automatically (via <img onerror>), with no interaction. Per-vector confirmation (each payload labelled, each verified in a browser):

Vector Trigger Cause
<img onerror> open file (auto) element text not escaped
<svg onload> (via title='"><svg ...>') open file (auto) attribute value not escaped (" breakout)
<a href=javascript:> click link URL scheme not filtered
onmouseover hover source attribute preserved as-is

Impact

Stored XSS caused by improper output encoding. Anyone who renders the HTML or text_as_html generated from an untrusted document is affected. In an ingestion pipeline where uploaded documents are parsed and a staff member reviews their contents in a web UI, a low-privileged or external submitter can inject malicious HTML; when a privileged reviewer later opens the parsed result, <img onerror> fires in their session with no interaction, leading to cross-record information disclosure and privileged actions.

Database specific 
{
    "cwe_ids":  [
        "CWE-116",
        "CWE-79"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-10-15T20:16:18Z",
    "nvd_published_at":  "2026-10-13T17:17:15Z",
    "severity":  "MODERATE"
}
References

Affected packages

PyPI / unstructured

Package

Name
unstructured
View open source insights on deps.dev
Purl
pkg:pypi/unstructured

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
0.24.1

Affected versions

0.*
0.0.1.dev0
0.2.0
0.2.1
0.2.2
0.2.3
0.2.4
0.2.5
0.2.6.dev1
0.3.0
0.3.1
0.3.2
0.3.3
0.3.4
0.3.5
0.4.0
0.4.1
0.4.2
0.4.3
0.4.4
0.4.6
0.4.7
0.4.8
0.4.9
0.4.10
0.4.11
0.4.12
0.4.13
0.4.14
0.4.15
0.4.16
0.5.0
0.5.1
0.5.2
0.5.3
0.5.4
0.5.6
0.5.7
0.5.8
0.5.9
0.5.10
0.5.11
0.5.12
0.5.13
0.6.0
0.6.1
0.6.2
0.6.3
0.6.4
0.6.5
0.6.6
0.6.7
0.6.8
0.6.9
0.6.10
0.6.11
0.7.0
0.7.1
0.7.2
0.7.3
0.7.4
0.7.5
0.7.6
0.7.7
0.7.8
0.7.9
0.7.10
0.7.11
0.7.12
0.8.0
0.8.1
0.8.3
0.8.4
0.8.5
0.8.6
0.8.7
0.8.8
0.9.0
0.9.1
0.9.2
0.9.3
0.10.0
0.10.1
0.10.2
0.10.4
0.10.5
0.10.6
0.10.7
0.10.8
0.10.9
0.10.10
0.10.11
0.10.12
0.10.13
0.10.14
0.10.15
0.10.16
0.10.18
0.10.19.dev18
0.10.19
0.10.20
0.10.21
0.10.22
0.10.23
0.10.24
0.10.25
0.10.26
0.10.27
0.10.28
0.10.29
0.10.30
0.11.0
0.11.1
0.11.2
0.11.4
0.11.5
0.11.6
0.11.7
0.11.8
0.12.0
0.12.2
0.12.3
0.12.4
0.12.5
0.12.6
0.13.0
0.13.1
0.13.2
0.13.3
0.13.4
0.13.5
0.13.6
0.13.7
0.14.0
0.14.2.dev1
0.14.2
0.14.3
0.14.4
0.14.5
0.14.6
0.14.7
0.14.8
0.14.9
0.14.10
0.15.0
0.15.1
0.15.3
0.15.5
0.15.6
0.15.7
0.15.8
0.15.9
0.15.10
0.15.12
0.15.13
0.15.14
0.16.0
0.16.1
0.16.2
0.16.3
0.16.4
0.16.5
0.16.6
0.16.7
0.16.8
0.16.9
0.16.10
0.16.11
0.16.12
0.16.13
0.16.14
0.16.15
0.16.16
0.16.17
0.16.19
0.16.20
0.16.21
0.16.22
0.16.23
0.16.24
0.16.25
0.17.0
0.17.2
0.18.1
0.18.2
0.18.3
0.18.5
0.18.6
0.18.7
0.18.9
0.18.11
0.18.13
0.18.14
0.18.15
0.18.18
0.18.20
0.18.21
0.18.24
0.18.26
0.18.27
0.18.31
0.18.32
0.20.2
0.20.6
0.20.8
0.21.0
0.21.1
0.21.2
0.21.5
0.22.6
0.22.10
0.22.12
0.22.16
0.22.18
0.22.20
0.22.21
0.22.22
0.22.23
0.22.26
0.22.27
0.22.28
0.22.29
0.22.30
0.22.31
0.22.32
0.23.0
0.23.1
0.24.0

Database specific

last_known_affected_version_range 
"<= 0.24.0"
source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-v5mq-3xhg-98m9/GHSA-v5mq-3xhg-98m9.json"