Spring Data REST SpEL Injection via Map Key in JSON Patch

Spring Data REST is vulnerable to SpEL expression injection through map-typed properties when processing JSON Patch (application/json-patch+json) requests. When a persistent entity exposes a Map-typed property, the JSON Pointer path segment used as the map key is embedded directly into a SpEL expression without sanitization or validation. Affected versions: Spring Data REST 3.7.0 through 3.7.19; 4.3.0 through 4.3.16; 4.4.0 through 4.4.14; 4.5.0 through 4.5.11; 5.0.0 through 5.0.5.