The OOXML parsing of the file indexer does not disable external entity resolution. A crafted xlsx or pptx document placed in an indexed directory can cause local files to be read or outbound HTTP requests to be performed, with the retrieved content being written to the search index.
The file indexer does not normalize the configured directory path. A backend user with permission to edit indexer configurations can index documents from arbitrary locations on the server file system through path traversal sequences.