ViewVC XSS vulnerability in revision view changed path "copyfrom" locations

Summary

ViewVC is a browser interface for CVS and Subversion version control repositories. Versions prior to 1.2.3 and 1.1.30 are vulnerable to cross-site scripting. The impact of this vulnerability is mitigated by the need for an attacker to have commit privileges to a Subversion repository exposed by an otherwise trusted ViewVC instance. The attack vector involves files with unsafe names (names that, when embedded into an HTML stream, would cause the browser to run unwanted code), which themselves can be challenging to create. Users should update to at least version 1.2.3 (if they are using a 1.2.x version of ViewVC) or 1.1.30 (if they are using a 1.1.x version). ViewVC 1.0.x is no longer supported, so users of that release lineage should implement one of the following workarounds. Users can edit their ViewVC EZT view templates to manually HTML-escape changed path "copyfrom paths" during rendering. Locate in your template set's `revision.ezt` file references to those changed paths, and wrap them with `[format "html"]` and `[end]`. For most users, that means that references to `[changes.copy_path]` will become `[format "html"][changes.copy_path][end]`. (This workaround should be reverted after upgrading to a patched version of ViewVC, else "copyfrom path" names will be doubly escaped.)