Deserialization of Untrusted Data
Tiki before 24.1, when the Spreadsheets feature is enabled, allows lib/sheet/grid.php PHP Object Injection because of an unserialize call.
CWE-502 - Deserialization of Untrusted Data
Deserialization of untrusted data vulnerabilities enable an attacker to replace or manipulate a serialized object, replacing it with malicious data. When the object is deserialized at the victim's end the malicious data is able to compromise the victim’s system. The exploit can be devastating, its impact may range from privilege escalation, broken access control, or denial of service attacks to allowing unauthorized access to the application's internal code and logic which can compromise the entire system.