SiYuan versions before v3.7.4 fail to enforce publish-access checks in the getBlockAttrs and batchGetBlockAttrs endpoints. Attackers can retrieve block attributes including names, aliases, memos, and custom fields from protected documents by sending POST requests with block IDs.

Affected: Go: github.com/siyuan-note/siyuan/kernel

**CVE:** This vulnerability corresponds to [CVE-2026-72803](https://nvd.nist.gov/vuln/detail/CVE-2026-72803).

### Summary

`POST /api/attr/getBlockAttrs` and `POST /api/attr/batchGetBlockAttrs` return a block's full attribute set (IAL) with no publish-access check. Both are `CheckAuth`-only, so they are reachable by the publish `RoleReader` token and by the anonymous account when `Publish.Auth.Enable` is `false`. An anonymous reader supplying a block ID receives the block's name, alias, memo, bookmark, tags, and every `custom-*` attribute including for blocks in publish-forbidden and password-protected documents. The batch variant accepts an ID list, making it a bulk extraction primitive.

### Details

Neither handler applies a filter:

```go // /api/attr/getBlockAttrs (router line 301) ret.Data = sql.GetBlockAttrs(id)

// /api/attr/batchGetBlockAttrs (router line 302) ret.Data = sql.BatchGetBlockAttrs(idList) ```

`sql.GetBlockAttrs` is a direct database read returning the block's entire IAL: `name`, `alias`, `memo`, `bookmark`, `tags`, and any `custom-*` key/value the user has set. Several of these are user-authored free text memos in particular are freeform notes attached to a block so this is document content, not merely structural metadata.

`batchGetBlockAttrs` takes an arbitrary list of block IDs in a single request, so an attacker holding a set of block IDs can sweep attributes across the entire workspace in one call.

**Guarded-sibling asymmetry.** The sibling…