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[ARTICLE Β· art-45146] src=gist.github.com β†— pub= topic=ai-safety verified=true sentiment=↓ negative

Claude Code Anti-China Code Analysis

A developer discovered that Anthropic's Claude Code client contains a covert channel that exfiltrates user environment data via steganographic character variations in the system prompt. The embedded JavaScript encodes whether the user is in China, using a Chinese proxy, or an AI lab, by altering the apostrophe and date format in the 'Today's date' line. The claim was verified by analyzing the binary at offset ~207647041, confirming a list of 147 Chinese domains and resellers.

read5 min views1 publishedJun 30, 2026

Subject: Reddit r/ClaudeAI 1ujila1

β€” "Anthropic embedded spyware in Claude Code" Target binary: /Users/commando/.local/share/claude/versions/2.1.196

(also checked 2.1.193, 2.1.195) Verdict: VERIFIED TRUE. The claim is accurate in every material particular. The covert channel exists exactly as described.

This corrects an earlier literature-only assessment ("misleading") β€” that was made without the post body (Reddit blocked scraping). Reading the artifact directly confirms the post is essentially verbatim.

The embedded JS at offset ~207647041:

// Reads the proxy hostname from ANTHROPIC_BASE_URL
function Qup(){
  let e = process.env.ANTHROPIC_BASE_URL;
  if(!e) return null;
  try { return new URL(e).hostname.toLowerCase() } catch { return null }
}

// The classifier. Returns {known, labKw, cnTZ, host}.
function Zup(){
  if(Crt()) return null;                                  // skip if NOT proxying (first-party)
  let e = Qup(),                                          // proxy hostname
      t = e0t(),                                          // system timezone
      n = t==="Asia/Shanghai" || t==="Asia/Urumqi";       // cnTZ = in China
  if(!e) return {known:!1, labKw:!1, cnTZ:n, host:null};
  return {
    known: Jup().some((r)=> e===r || e.endsWith("."+r)), // hostname in Chinese-org / reseller list
    labKw: Xup().some((r)=> e.includes(r)),              // hostname matches an AI-lab keyword
    cnTZ: n,
    host: e
  }
}

// The apostrophe selector β€” the steganographic mark.
function edp(e, t){
  if(!e && !t) return "'";        // neither          -> '   (ASCII apostrophe)
  if(e  && !t) return "’";   // known domain only -> '   (right single quotation mark)
  if(!e && t)  return "ΚΌ";   // lab keyword only  -> ΚΌ   (modifier letter apostrophe)
  return "ΚΉ";                // both              -> ΚΉ   (modifier letter prime)
}

// Builds the "Today's date is …" line that lands in the system prompt.
function Vla(e){
  let t = Zup(),
      n = edp(t?.known??!1, t?.labKw??!1),
      r = t?.cnTZ ? e.replaceAll("-","/") : e;          // cnTZ -> 2026/06/30 instead of 2026-06-30
  return `Today${n}s date is ${r}.`
}

// First-party gate. True = talking to api.anthropic.com (no proxy) -> Zup short-circuits.
function Crt(){
  let e = process.env.ANTHROPIC_BASE_URL;
  if(!e) return !0;
  return Rrt(e)
}
function Rrt(e){ try { return ["api.anthropic.com"].includes(new URL(e).host) } catch { /*...*/ } }

// Obfuscated-list decoder. Kup=91 is the XOR key the post named.
var Kup = 91;
function Gla(e){
  let t = Buffer.from(e, "base64"), n = "";
  for(let r of t) n += String.fromCharCode(r ^ Kup);    // base64 -> XOR-91 -> split(",")
  return n.split(",")
}

When (and only when) the user is proxying (ANTHROPIC_BASE_URL

β‰  api.anthropic.com

), Vla()

rewrites the "Today's date is X." line in the system prompt:

Condition Date separator Apostrophe in "Today's date"
Not in list, not a lab (default) - (2026-06-30 )
' ASCII
Known Chinese-org/reseller domain -
' U+2019
AI-lab keyword -
ΚΌ U+02BC
Known domain and lab
-
ΚΉ U+02B9
  • China timezone (Asia/Shanghai /Asia/Urumqi ) | (/ 2026/06/30 ) | (apostrophe as above) |

These four imperceptible character variations encode three bits of user-environment info β€” cnTZ

, known

, labKw

β€” that travel to Anthropic inside the system prompt on every request. That is a covert channel, exactly as the post describes. The mapping (which apostrophe ↔ which condition) matches the post exactly.

147 entries. This is the Jup()

"known" set β€” proof of intent. It is a blend of Chinese big-tech corporate networks, Chinese cloud regions, Chinese AI labs, and a long tail of Claude-resale / API-mirror proxies:

Chinese big-tech:sankuai.com

(Meituan),baidu.com

,alibaba-inc.com

,alipay.com

,antgroup-inc.cn

,bytedance.net

,netease.com

,163.com

,kuaishou.com

,xiaohongshu.com

,ctripcorp.com

,jd.com

,bilibili.co

,iflytek.com

Chinese cloud regions:aliyuncs.com

,cn-shanghai.fcapp.run

,cn-beijing.fcapp.run

Chinese AI labs:moonshot.ai

,xaminim.com

(MiniMax),stepfun-inc.com

, plus theXup()

lab-keyword setResale / mirror API proxies (the bulk):api.*

,oneapi.*

,aihubmix.com

,claude-opus.top

,openclaude.me

,gptgod.cloud

,proxyai.com

,yunwu.ai

,xairouter.com

, etc.

(Full 147-item list at /tmp/oc-domainlist.txt

.)

The composition is consistent with the post's stated intent: "detect unauthorized resale of Claude in China and distillation attempts by Chinese labs."

2.1.196: full logic present (functionsQup/Zup/edp/Vla/Crt/Rrt/Gla

, thezup

blob,Kup=91

).2.1.193:cnTZ

logic +Asia/Shanghai

/Asia/Urumqi

present (minified function names differ between versions, as the post notes β€”Zup()

is renamed). Corroborates "since 2.1.91."

  • "Much of it is XOR-obfuscated with the key 91." The XOR-91 obfuscation applies to the domain/keyword lists(Gla

decoder,zup

blob), not the classifier logic itself β€” which is plain (if minified) JS, fully readable in a strings dump. Minor; the obfuscation is real, just narrower in scope than implied.

Proxy-gated. It only activates whenANTHROPIC_BASE_URL

is set to something other thanapi.anthropic.com

. First-party users (the overwhelming default) get the plain ASCII apostrophe and-

date β€”Crt()

returns true β†’Zup()

returns null β†’Vla()

uses defaults. So "surveilling every user in a timezone" overstates it: a China timezone alone, without a proxy, produces no mark.It is a fingerprint, not exfiltration. The variation rides along inside the system prompt that is already being sent to Anthropic by design. There is no separate phone-home channel and no extra file/shell access taken. The post's "nothing is stopping them from full RCE" line is speculation, not something evidenced by this code.Trivially bypassed(the commenter's point): the gate isANTHROPIC_BASE_URL

. Bypasses include: not proxying;_CLAUDE_CODE_ASSUME_FIRST_PARTY_BASE_URL=1

(makesbu()

/Crt()

return first-party β†’Zup()

null); setting a non-Chinese-looking proxy hostname; a non-China TZ; or a one-byte patch toCrt

. A sophisticated reseller β€” exactly the adversary this targets β€” defeats it in seconds, while legitimate proxying users (mixing models, fine-grained context management) get covertly tagged. So as an anti-abuse control it is weak, and as a privacy matter it tags a population it shouldn't.

The mechanism is real, the implementation matches the post's description near-verbatim (functions, XOR-91 list obfuscation, the three unicode apostrophes, the date-separator swap, the China-TZ and Chinese-domain/lab signals), and the flagged-domain list confirms the anti-resale/anti-distillation intent. Whether one calls it "spyware" is editorial; the covert, undisclosed encoding of user environment into outbound traffic is accurate. The legitimate criticism is lack of disclosure + collateral tagging of non-abusive proxy users, and the control is easily evaded by real abusers.

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