Grav - Stored CSS Injection via Markdown Image resize() Action

Grav before 2.0.0 (affected through 2.0.0-rc.9 and the 2.0 branch) contains a stored CSS injection vulnerability in the Markdown image resize() media action. Prior media hardening rejects direct ?style= payloads and unsafe attribute() fallbacks, but the resize() action in Excerpts::processMediaActions() writes caller-controlled values directly into the image's styleAttributes. A lower-privileged content editor who can edit page Markdown can store a crafted image URL with semicolon-delimited CSS declarations in the resize parameters, which are rendered into the final <img style=...> attribute when a higher-privileged reviewer/admin views the page or preview. This does not require JavaScript execution but enables UI redress/overlay and content-manipulation attacks (e.g., a full-viewport fixed overlay). Fixed in 2.0.0.

Source published

8 Jul 2026 13:49:12 UTC

Source modified

8 Oct 2026 15:23:30 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 4.0 · 4.8 CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

CVSS 3.1 · 4.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N