Romeo gives the capability to reach high code coverage of Go ≥1.20 apps by helping to measure code coverage for functional and integration tests within GitHub Actions. Prior to version 0.2.2, the `sanitizeArchivePath` function in `webserver/api/v1/decoder.go` (lines 80-88) is vulnerable to a path traversal bypass due to a missing trailing path separator in the `strings.HasPrefix` check. A crafted tar archive can write files outside the intended destination directory. Version 0.2.2 fixes the issue.

Affected: Go: github.com/ctfer-io/romeo/webserver

## Summary

The `sanitizeArchivePath` function in `webserver/api/v1/decoder.go` (lines 80-88) is vulnerable to a path traversal bypass due to a missing trailing path separator in the `strings.HasPrefix` check. A crafted tar archive can write files outside the intended destination directory.

## Vulnerable Code

File: `webserver/api/v1/decoder.go`, lines 80-88

```go func sanitizeArchivePath(d, t string) (v string, err error) { v = filepath.Join(d, t) if strings.HasPrefix(v, filepath.Clean(d)) { return v, nil } return "", &ErrPathTainted{ Path: t, } } ```

The function is called at line 48 inside `[*Decompressor].Unzip`, which is invoked by `Decode` (line 80) during execution of the webserver CLI (command `download`).

## Root Cause

`strings.HasPrefix(v, filepath.Clean(d))` does not append a trailing `/` to the directory prefix, causing a **directory name prefix collision**. If the destination is `/home/user/extract-output` and a tar entry is named `../extract-outputevil/pwned`, the joined path `/home/user/extract-outputevil/pwned` passes the prefix check — it starts with `/home/user/extract-output` — even though it is entirely outside the intended directory.

## Steps to Reproduce

1. **Deploy Romeo**. A measured app writes its coverage data.

2. **Place the PoC zip on the PVC.** Any pod with write access to the `ReadWriteMany` PVC (or the webserver itself) copies a `poc-path-traversal.tar` into the `coverdir` mount path. The archive contains legitimate coverage fi…