conf/firefox-forbidden-policies.js

@@ -67,7 +67,7 @@ lockPref(
 	"privacy.fingerprintingProtection.overrides",
 	"+AllTargets,-KeyboardEvents,-CSSPrefersColorScheme,-CSSPrefersReducedMotion,-JSDateTimeUTC,-FontVisibilityBaseSystem,-FontVisibilityRestrictGenerics",
 );
-pref("browser.display.use_document_fonts", 0);
+lockPref("browser.display.use_document_fonts", 0);
 
 // Letterboxing from Tor Browser, I like it in general.
 lockPref("privacy.resistFingerprinting.letterboxing", true);

etc/firefox/policies/policies.json

@@ -630,7 +630,7 @@
 			},
 			"browser.display.use_document_fonts": {
 				"Comment": "Are webpages allowed to set their own fonts by default? 0 forbids them. See also browser.display.use_document_fonts.icon_font_allowlist for what webpages are allowed to set. If changing this, see also fingerprinting overrides",
-				"Status": "user",
+				"Status": "locked",
 				"Type": "number",
 				"Value": 0
 			},