Resolvesforgejo/forgejo#6039
## Checklist
The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).
### Tests
- I added test coverage for Go changes...
- [x] in their respective `*_test.go` for unit tests.
- [ ] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I added test coverage for JavaScript changes...
- [ ] in `web_src/js/*.test.js` if it can be unit tested.
- [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).
### Documentation
- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.
### Release notes
- [ ] I do not want this change to show in the release notes.
- [x] I want the title to show in the release notes with a link to this pull request.
- [ ] I want the content of the `release-notes/<pull request number>.md` to be be used for the release notes instead of the title.
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## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Bug fixes
- [PR](https://codeberg.org/forgejo/forgejo/pulls/8850): <!--number 8850 --><!--line 0 --><!--description YWxsb3cgRm9yZ2VqbyBBY3Rpb25zIGVudmlyb25tZW50IHZhcmlhYmxlcyBzdGFydGluZyB3aXRoIENJ-->allow Forgejo Actions environment variables starting with CI<!--description-->
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Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8850
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>
The web route to update and delete variables of runners did not check if
the ID that was given belonged to the context it was requested in, this
made it possible to update and delete every existing runner variable of
a instance for any authenticated user.
The code has been reworked to always take into account the context of
the request (owner and repository ID).
