# CVE-2020-27783: lxml vulnerable to Cross-site Scripting

Source: https://junglewise.ai/threats/cve-2020-27783-lxml-vulnerable-to-cross-site-scripting  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2020-12-03  
License: CC BY 4.0 with a link back

CVE-2020-27783 · Severity: low · CVSS 3.1 · Published 2020-12-03

A XSS vulnerability was discovered in python-lxml's clean module. The module's parser didn't properly imitate browsers, which caused different behaviors between the sanitizer and the user's page. A remote attacker could exploit this flaw to run arbitrary HTML/JS code.

Technologies: [lxml (PyPI)](https://junglewise.ai/threats/technologies/lxml). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2020-27783 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2020-27783 being exploited in the wild.

**How severe is CVE-2020-27783?** Low severity, with a CVSS score of 3.1, published 3 December 2020.

**Which products and versions are affected?** lxml (PyPI) ECOSYSTEM:introduced=0,fixed=4.6.2, ECOSYSTEM:introduced=1.2,fixed=4.6.2.

**Is there a fix for CVE-2020-27783?** Yes. lxml (PyPI): upgrade to 4.6.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2020-27783?** Check whether you run lxml (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- lxml (PyPI): upgrade to 4.6.2 or later

  ```sh
  pip install "lxml>=4.6.2"
  ```


## Affected products

- lxml (PyPI) ECOSYSTEM:introduced=0,fixed=4.6.2, ECOSYSTEM:introduced=1.2,fixed=4.6.2

## Identifiers

- CVE-2020-27783
- GHSA-pgww-xf46-h92r
- PYSEC-2020-62

## Related threats

- [lxml XXE in iterparse and ETCompatXMLParser](https://junglewise.ai/threats/cve-2026-41066-lxml-xxe-in-iterparse-and-etcompatxmlparser)
- [lxml NULL Pointer Dereference allows attackers to cause a denial of service](https://junglewise.ai/threats/cve-2022-2309-lxml-null-pointer-dereference-allows-attackers-to-cause-a-denial)
- [lxml's HTML Cleaner allows crafted and SVG embedded scripts to pass through](https://junglewise.ai/threats/cve-2021-43818-lxml-s-html-cleaner-allows-crafted-and-svg-embedded-scripts-to)
- [lxml vulnerable to Cross-Site Scripting](https://junglewise.ai/threats/cve-2021-28957-lxml-vulnerable-to-cross-site-scripting)
- [Improper Neutralization of Input During Web Page Generation in LXML](https://junglewise.ai/threats/cve-2018-19787-improper-neutralization-of-input-during-web-page-generation-in)