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.

The vulnerability allows an attacker to access sensitive files on the server by confusing the agent with incorrect file names. When a user requests the content of a file with a misspelled name, the agent attempts to correct the command and inadvertently reveals the content of the intended file, such as /etc/passwd. This can lead to unauthorized access to sensitive information and potential server compromise.