XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. The XWiki Crypto API will generate X509 certificates signed by default using SHA1 with RSA, which is not considered safe anymore for use in certificate signatures, due to the risk of collisions with SHA1. The problem has been patched in XWiki version 13.10.6, 14.3.1 and 14.4-rc-1. Since then, the Crypto API will generate X509 certificates signed by default using SHA256 with RSA. Administrators are advised to upgrade their XWiki installation to one of the patched versions. If the upgrade is not possible, it is possible to patch the module xwiki-platform-crypto in a local installation by applying the change exposed in 26728f3 and re-compiling the module.