docs: update CHANGELOG

Signed-off-by: Xe Iaso <me@xeiaso.net>

.github/actions/spelling/expect.txt

@@ -63,6 +63,7 @@ Cromite
 crt
 Cscript
 daemonizing
+dayjob
 DDOS
 Debian
 debrpm
@@ -98,6 +99,7 @@ Factset
 fastcgi
 fediverse
 ffprobe
+financials
 finfos
 Firecrawl
 flagenv
@@ -285,6 +287,7 @@ SVCNAME
 tagline
 tarballs
 tarrif
+taviso
 tbn
 tbr
 techaro

docs/blog/2025-08-18-funding-update/index.mdx

@@ -0,0 +1,60 @@
+---
+slug: 2025/funding-update
+title: Funding update
+authors: [xe]
+tags: [funding]
+image: around-the-bend.webp
+---
+
+![](./around-the-bend.webp)
+
+As we finish up work on [all of the features in the next release of Anubis](/docs/CHANGELOG#unreleased), I took a moment to add up the financials and here's an update on the recurring revenue of the project. Once I reach the [$5000 per month](https://github.com/TecharoHQ/anubis/discussions/278) mark, I can start reducing hours at my dayjob and start to make working on Anubis my full time job.
+
+{/* truncate */}
+
+Note that this only counts _recurring_ revenue (subscriptions to [BotStopper](/docs/admin/botstopper) and monthly repeating donations). Every one of the one-time donations I get is a gift and I am grateful for them, but I cannot make critically important financial decisions off of sporadic one-time donations.
+
+:::note
+
+All currency figures in this article are USD (United States Dollars) unless denoted otherwise.
+
+:::
+
+Here's the funding breakdown by income stream:
+
+```mermaid
+pie title Funding update August 2025
+    "GitHub Sponsors" : 3500
+    "Patreon" : 1500
+    "Liberapay" : 100
+    "Remaining" : 4800
+```
+
+Assuming that some of my private support contracts and other sales effort go through, this will slightly change the shapes of this (a new pie chart segment will emerge for "Manual invoices"), but I am halfway there. This is a huge bar to pass and as it stands right now this is just enough income to pay for my monthly rent (not accounting for tax).
+
+As a reminder, here's the rough plan for the phases I want to hit based on the _recurring_ donation totals:
+
+| Monthly donations           | Details                                                                                                                                                                     |
+| :-------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| $0-5,000 per month          | Anubis is a nights and weekends project based on how much spare time and energy I have.                                                                                     |
+| $5,000-10,000 per month     | Anubis gets 1-2 days per week of my time put into it consistently and I go part-time at my dayjob.                                                                          |
+| $10,000-15,000 per month    | Anubis becomes my full time job. Features that are currently exclusive to [BotStopper](/docs/admin/botstopper/) start to trickle down to the open source version of Anubis. |
+| $15,000 per month and above | I start planning hiring for Techaro.                                                                                                                                        |
+
+If your organization benefits from Anubis, please consider donating to the project in order to make this sustainable. The fewer financial problems I have means the more that Anubis can become better.
+
+## New funding platform: Liberapay
+
+After many comments about the funding options, I have set up [Liberapay](https://liberapay.com/Xe/) as an option to receive donations. Additional funding targets will be added to Liberapay as soon as I hear back from my accountant with more information. All money received via Liberapay goes directly towards supporting the project.
+
+## Next goals
+
+Here's my short term goals for the immediate future:
+
+1. Finish [Thoth](/docs/admin/thoth/) and run a backfill to mass issue API keys.
+2. Document and publish the writeup for the multi-region Google Cloud spot instance setup that Thoth is built upon.
+3. Release v1.22.0 of Anubis with Traefik support and other important fixes.
+4. Continue growing the project into a sustainable business.
+5. Work through the [blog backlog](https://github.com/TecharoHQ/anubis/issues?q=is%3Aissue%20state%3Aopen%20label%3Ablog) to document the thoughts behind Anubis and how parts of it work.
+
+Thank you for supporting Anubis! It's only going to get better from here.

docs/docs/CHANGELOG.md

@@ -39,6 +39,22 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - The word "hack" has been removed from the translation strings for Anubis due to incidents involving people misunderstanding that word and sending particularly horrible things to the project lead over email.
 - Bump AI-robots.txt to version 1.39
 
+### Security-relevant changes
+
+#### Fix potential double-spend for challenges
+
+Anubis operates by issuing a challenge and having the client present a solution for that challenge. Challenges are identified by a unique UUID, which is tored in the database.
+
+The problem is that a challenge could potentially be used twice by a dedicated attacker making a targeted attack against Anubis. Challenge records did not have a "spent" or "used" field. In total, a dedicated attacker could solve a challenge once and reuse that solution across multiple sessions in order to mint additional tokens.
+
+This was fixed by adding a "spent" field to challenges in the data store. When a challenge is solved, that "spent" field gets set to `true`. If a future attempt to solve this challenge is observed, it gets rejected.
+
+With the advent of store based challenge issuance in [#749](https://github.com/TecharoHQ/anubis/pull/749), this means that these challenge IDs are [only good for 30 minutes](https://github.com/TecharoHQ/anubis/blob/e8dfff635015d6c906dddd49cb0eaf591326092a/lib/anubis.go#L130-L135d). Websites using the most recent version of Anubis have limited exposure to this problem.
+
+Websites using older versions of Anubis have a much more increased exposure to this problem and are encouraged to keep this software updated as often and as frequently as possible.
+
+Thanks to [@taviso](https://github.com/taviso) for reporting this issue.
+
 ### Breaking changes
 
 - The "slow" frontend solver has been removed in order to reduce maintenance burden. Any existing uses of it will still work, but issue a warning upon startup asking administrators to upgrade to the "fast" frontend solver.

lib/anubis.go

@@ -454,6 +454,12 @@ func (s *Server) PassChallenge(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if chall.Spent {
+		lg.Error("double spend prevented", "reason", "double_spend")
+		s.respondWithError(w, r, fmt.Sprintf("%s: %s", localizer.T("internal_server_error"), "double_spend"))
+		return
+	}
+
 	impl, ok := challenge.Get(chall.Method)
 	if !ok {
 		lg.Error("check failed", "err", err)
@@ -527,6 +533,12 @@ func (s *Server) PassChallenge(w http.ResponseWriter, r *http.Request) {
 
 	s.SetCookie(w, CookieOpts{Path: cookiePath, Host: r.Host, Value: tokenString})
 
+	chall.Spent = true
+	j := store.JSON[challenge.Challenge]{Underlying: s.store}
+	if err := j.Set(r.Context(), "challenge:"+chall.ID, *chall, 30*time.Minute); err != nil {
+		lg.Debug("can't update information about challenge", "err", err)
+	}
+
 	challengesValidated.WithLabelValues(rule.Challenge.Algorithm).Inc()
 	lg.Debug("challenge passed, redirecting to app")
 	http.Redirect(w, r, redir, http.StatusFound)

lib/challenge/challenge.go

@@ -9,4 +9,5 @@ type Challenge struct {
 	RandomData string            `json:"randomData"` // The random data the client processes
 	IssuedAt   time.Time         `json:"issuedAt"`   // When the challenge was issued
 	Metadata   map[string]string `json:"metadata"`   // Challenge metadata such as IP address and user agent
+	Spent      bool              `json:"spent"`      // Has the challenge already been solved?
 }