Path Traversal via Symbolic Links in run-llama/llama_index

A vulnerability in the `ObsidianReader` class of the run-llama/llama_index repository, versions 0.12.23 to 0.12.28, allows for arbitrary file read through symbolic links. The `ObsidianReader` fails to resolve symlinks to their real paths and does not validate whether the resolved paths lie within the intended directory. This flaw enables attackers to place symlinks pointing to files outside the vault directory, which are then processed as valid Markdown files, potentially exposing sensitive information.