Description
wp_kses_bad_protocol in wp-includes/kses.php in WordPress before 5.3.1 mishandles the HTML5 colon named entity, allowing attackers to bypass input sanitization, as demonstrated by the javascript: substring.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | wordpress | 5.3.2+dfsg1-1 | — |
| Debian 13 | wordpress | 5.3.2+dfsg1-1 | — |
| Debian 12 | wordpress | 5.3.2+dfsg1-1 | — |
| Debian 10 | wordpress | 5.0.4+dfsg1-1+deb10u1 | DSA-4599-1 |
| Debian 8 | wordpress | 4.1.29+dfsg-0+deb8u1 | DLA-2067-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | wordpress | No fix yet | — |
| Ubuntu 16.04 LTS | wordpress | No fix yet | — |
Advisories 2
- DSA-4599-1 wordpress - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2067-1 wordpress - security update Debian Security (DSA / DLA) · Mar 9, 2026
References
- https://wordpress.org/news/2019/12/wordpress-5-3-1-security-and-maintenance-release/
- https://github.com/WordPress/wordpress-develop/commit/b1975463dd995da19bb40d3fa0786498717e3c53
- 20200108 [SECURITY] [DSA 4599-1] wordpress security update mailing-list
- DSA-4599 vendor-advisory
- [debian-lts-announce] 20200114 [SECURITY] [DLA 2067-1] wordpress security update mailing-list
- DSA-4677 vendor-advisory