Activepieces, an open‑source AI workflow automation platform, contained a flaw in its /v1/step-files/signed download endpoint prior to version 0.83.0. The endpoint validated JWTs only against the shared signing secret but omitted a check of the token's audience claim and also missed a null‑check on the decoded fileId, resulting in weaknesses identified as CWE-345 and CWE-639. Consequently, any authenticated user possessing a valid Activepieces JWT could request a signed step‑file download and receive a file belonging to another tenant. The file returned was simply the first PostgreSQL record matching type = FLOW_STEP_FILE, so the attacker could not target a specific tenant or file but could still read arbitrary step‑file attachments belonging to other tenants. The vulnerability does not affect file integrity or availability; its impact is limited to confidential data disclosure.

All deployments of Activepieces with releases earlier than 0.83.0 are affected. The issue is fixed in release 0.83.0 and later versions.

The CVSS score of 5.3 denotes moderate severity, and the EPSS score of less than 1 % indicates a low likelihood of exploitation at the time of this analysis. The vulnerability is not listed in CISA’s KEV catalog. Exploitation requires an attacker to hold any valid Activepieces JWT. Because the JWT is not bound to a specific audience, legacy tokens lacking that claim can be used; however, the attacker cannot select a particular tenant or file, only any file that the database happens to return first. Thus the primary risk is confidentiality loss of cross‑tenant file data with no integrity or availability impacts.