CVE-2026-87811

SiYuan before v3.8.2 Stored XSS via notebook template paths

HIGH
7.3
CVSS Score
Published: September 9, 2026 at 11:20 AM UTC
Updated: September 9, 2026 at 08:37 PM UTC
2 products affected across 2 vendorsSiyuanSiyuan

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Severity
HIGH7.3
Exploit prediction
EPSS 0.4%
SSVC
PoC

Description

SiYuan before v3.8.2 inserts persisted notebook template paths into HTML input value attributes without proper attribute encoding. Attackers can craft malicious template paths that break out of the attribute context and execute JavaScript when a victim opens notebook configuration, enabling same-origin API requests and application state manipulation.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 3.8.2
Affected range stops below 3.8.2, so it looks safe — our inference, not a vendor statement
v < 3.8.2
Vendor states this is fixed in 3.8.2 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCPoCNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.3HIGHVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-79

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