Also allow local files

config/config.sample.php

@@ -130,7 +130,7 @@ $CONFIG = array(
 "remember_login_cookie_lifetime" => 60*60*24*15,
 
 /* Custom CSP policy, changing this will overwrite the standard policy */
-"custom_csp_policy" => "default-src \'self\'; script-src \'self\' \'unsafe-eval\'; style-src \'self\' \'unsafe-inline\'; frame-src *; img-src *; font-src data:",
+"custom_csp_policy" => "default-src \'self\'; script-src \'self\' \'unsafe-eval\'; style-src \'self\' \'unsafe-inline\'; frame-src *; img-src *; font-src \'self\' data:",
 
 /* The directory where the user data is stored, default to data in the owncloud
  * directory. The sqlite database is also stored here, when sqlite is used.

lib/template.php

@@ -192,7 +192,7 @@ class OC_Template{
 
 		// Content Security Policy
 		// If you change the standard policy, please also change it in config.sample.php
-		$policy = OC_Config::getValue('custom_csp_policy',  'default-src \'self\'; script-src \'self\' \'unsafe-eval\'; style-src \'self\' \'unsafe-inline\'; frame-src *; img-src *; font-src data:');
+		$policy = OC_Config::getValue('custom_csp_policy',  'default-src \'self\'; script-src \'self\' \'unsafe-eval\'; style-src \'self\' \'unsafe-inline\'; frame-src *; img-src *; font-src \'self\' data:');
 		header('Content-Security-Policy:'.$policy); // Standard
 		header('X-WebKit-CSP:'.$policy); // Older webkit browsers