Spent several hours dealing with the problem of http proxies, which
bypassed the IP address checks added to prevent the security hole.
Eventually got it filtering out http proxies located on private IP
addresses.

Other than the question of what to do about external special remotes
that may be vulerable to related problems, it looks like the security
hole is all closed off in git-annex now.

Added a new page [[security]] with details of this and past security holes
in git-annex.

Several people I reached out to for help with special remotes have gotten
back to me, and we're discussing how the security hole may affect them and
what to do. Thanks especially to Robie Basak and Daniel Dent for their
work on security analysis.

Also prepared a minimal backport of the security fixes for the git-annex in
Debian stable, which will probably be more palatable to their security team
than the full 2000+ lines of patches I've developed so far. 
The minimal fix is secure, but suboptimal; it prevents even safe urls from
being downloaded from the web special remote by default.

[[!meta date="June 18 2018 4:00 pm"]]
