Ubuntu Security Notice 2348-1 – It was discovered that APT did not re-verify downloaded files when the If-Modified-Since wasn’t met. It was discovered that APT did not invalidate repository data when it switched from an unauthenticated to an authenticated state. It was discovered that the APT Acquire::GzipIndexes option caused APT to skip checksum validation. This issue only applied to Ubuntu 12.04 LTS and Ubuntu 14.04 LTS, and was not enabled by default. Various other issues were also addressed.