CVE-2026-14574: Improperly Controlled Modification of Object Prototype Attributes

In Eclipse Theia versions 0.7.0 and up until including 1.73.1, the PreferenceUtils.merge function in @theia/core recursively merges preference values without rejecting prototype-related keys proto, constructor, prototype. Because this function is invoked by PreferenceServiceImpl.doResolve for eve...