Weblate vulnerable to XSS via crafted Markdown

Description

Impact

The Markdown renderer used in user comments and other user-provided content didn't properly sanitize some attributes.

Patches

  • https://github.com/WeblateOrg/weblate/pull/19259

Workarounds

Even though the attacker might be able to inject code into the HTML, the Weblate's strict CSP should mitigate the risks.

Acknowlegement

Michal Čihař has identified and fixed this vulnerability.

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-05-07 00:04:26 UTC
Updated
2026-05-08 21:47:44 UTC
GitHub reviewed
2026-05-07 00:04:26 UTC
NVD published
2026-05-07

EPSS Score

Score Percentile
0.03% 8.77%

CVSS Scores

Base score Version Severity Vector
4.3 3.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

CWEs

CWE id Name
CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

Credits

  • nijel (finder)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
pip weblate < 5.17.1 5.17.1

References

cvelogic Threat Intelligence