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CVE-2018-10101: Before WordPress 4.9.5, the URL validator assumed URLs with the hostname localhost were on the same host as the WordPress server.

medium Affects WordPress core. Feed 2026.10.29.4, updated 2026-10-29; published ; advisory modified .

Before WordPress 4.9.5, the URL validator assumed URLs with the hostname localhost were on the same host as the WordPress server.

Package
WordPress core WordPress
Affected versions
<4.9.5
Fixed in
4.9.5
Severity
medium  CVSS 6.1
Exploitation
not on CISA KEV · EPSS 3% (85.5th percentile)
Published
2018-04-16
Source
nvd

References

CWE-601
NVD recordWordPress core advisories

Am I affected?

Find out in one command. phpwarden checks your WordPress install against this advisory and 20,000+ others, ranked by real-world exploitation (CISA KEV + EPSS). Free, offline, open data.

# PHP projects (recommended)
composer require --dev phpwarden/phpwarden
# then
vendor/bin/phpwarden wordpress /var/www/html

# or, without Composer
pipx install phpwarden   &&   phpwarden wordpress /var/www/html

Or keep it checked automatically with the GitHub Action or a nightly cron; see WordPress docs.

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