Apple has released iOS 13.2.3 and iPadOS 13.2.3. Go to Settings —> General —> Software Update on your iPhone / iPad to install them.
According to Apple's release notes, the updates:
- Fix an issue where system search and search within Mail, Files, and Notes might not work;
- Address an issue where photos, links, and other attachments might not display in the Messages details view;
- Fix an issue that could prevent apps from downloading content in the background;
- Resolves issues that may prevent Mail from fetching new messages, and fail to include and quote original message content in Exchange accounts.