Markdown preview cannot display images outside current directory on Linux

[liolok]

Versions

• VSCode Version: 1.29.1
• OS Version:
  • Arch Linux
  • A fresh installed elementary OS Juno 5.0 on VMware (based on Ubuntu 18.04 LTS, should be regarded as the same Linux distro in this issue)

Steps to Reproduce

1. Open a markdown file for example /path/to/this/file.md, which is in directory /path/to/this/;
2. Add a local image which is wherever outside /path/to/this/, for example /path/to/that/image.png (or ../that/image.png to current directory /path/to/this/);
3. Open preview of this markdown file, image just won't show up.

Screenshots

Markdown and image files' location relationship is displayed on the left half of this screenshot.

Extensions

Does this issue occur when all extensions are disabled?: Yes, and extension "Markdown Preview Enhanced" has the same issue.

More info I want to submit

This issue occurs on both Arch Linux and elementary OS: On Arch I tried community/code, archlinuxcn/visual-studio-code-bin and aur/visual-studio-code-insiders; on elementary OS I just followed the documentation Running Visual Studio Code on Linux and ran the command $ sudo apt install ./code_1.29.1-1542309157_amd64.deb.

I've also changed "Preview Security Settings" and even disabled it, still the same.

Once before I used the ../docs/image.png link on VSCode for Windows and the behavior was expected, so it seems to be an issue on VSCode for Linux for now.

[mjbvz]

This is by design. Even if you disable markdown security settings, we only allow the preview to load data from inside the current workspace. This helps to somewhat lessen the impact of opening with untrusted content with security settings disabled