In GLPI before version 9.5.0, the encryption algorithm used is insecure. The security of the data encrypted relies on the password used, if a user sets a weak/predictable password, an attacker could decrypt data. This is fixed in version 9.5.0 by using a more secure encryption library. The library chosen is sodium.
https://github.com/glpi-project/glpi/security/advisories/GHSA-7xwm-4vjr-jvqh