Summary
Authenticated users can craft a filter string used to cause a SQL injection.
Details
Give all details on the vulnerability. Pointing to the incriminated source code is very helpful for the maintainer.
This code does not look to sanitize inputs: https://github.com/pimcore/pimcore/blob/c721a42c23efffd4ca916511ddb969598d302396/models/DataObject/ClassDefinition/Data/Extension/RelationFilterConditionParser.php#L29-L47
c.f. with https://github.com/pimcore/pimcore/blob/c721a42c23efffd4ca916511ddb969598d302396/models/DataObject/ClassDefinition/Data/Multiselect.php#L332-L347
PoC
Complete instructions, including specific configuration details, to reproduce the vulnerability.
Impact
What kind of vulnerability is it? Who is impacted?