Grocy - Stored XSS via HTMLPurifier Output Double-Decode

Grocy's API request-body parser (controllers/Api/BaseApiController.php, GetParsedAndFilteredRequestBody) purifies incoming field values with HTMLPurifier, then manually reverses HTML-entity encoding of the resulting output by replacing &amp;lt;, &amp;gt;, and &amp;amp; back to <, >, and & immediately after purification.

Bernd Bestel grocy v4.6.0 was discovered to contain a SQL injection vulnerability in the product-group parameter at /stockreports/spendings. This vulnerability allows attackers to access sensitive database information via a crafted SQL statement.

Stored XSS in Grocy

Versions of Grocy <= 2.7.1 are vulnerable to Cross-Site Scripting via the Create Shopping List module, that is rendered upon deleting that Shopping List. The issue was also found in users, batteries, chores, equipment, locations, quantity units, shopping locations, tasks, taskcategories, product groups, recipes and products. Authentication is required to exploit these issues and Grocy should not be publicly exposed. The linked reference details a proof-of-concept.