vulnerability / NVI-00008922 / Revision 3
Parse Server vulnerable to stored XSS via malformed Content-Type bypassing file upload extension blocklist
GitHub lists this reviewed advisory for parse-server, parse-server. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
0.415%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.35785. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
parse-server
source listed>= 9.0.0, < 9.10.0-alpha.2
### Impact Parse Server's file upload validation uses the `fileUpload.fileExtensions` option (enabled by default with a blocklist) to reject files that browsers may render as active content, mitigating stored cross-site scripting (XSS). When an uploaded file's extension is not recognized by the `mime` package, Parse Server preserves the client-supplied `Content-Type` and passes it to the storage adapter. A malformed `Content-Type` that is not a valid `type/subtype` media type — for example `image` (no subtype), `image/` (empty subtype), or `image//svg+xml` (invalid token) — bypassed the blocklist and was stored unchanged. On storage adapters that persist and serve the uploaded `Content-Type` (such as Amazon S3, Google Cloud Storage, or Azure Blob Storage), a browser cannot parse the malformed `Content-Type` and falls back to MIME-sniffing the file content; a file whose body begins with HTML markup is then rendered as HTML, executing any embedded script in the application's origin. This allows a user permitted to upload files to store content that executes as script against other users who open the file URL. The default GridFS storage adapter is not affected, as it recomputes the `
parse-server
source listed<= 8.6.83
### Impact Parse Server's file upload validation uses the `fileUpload.fileExtensions` option (enabled by default with a blocklist) to reject files that browsers may render as active content, mitigating stored cross-site scripting (XSS). When an uploaded file's extension is not recognized by the `mime` package, Parse Server preserves the client-supplied `Content-Type` and passes it to the storage adapter. A malformed `Content-Type` that is not a valid `type/subtype` media type — for example `image` (no subtype), `image/` (empty subtype), or `image//svg+xml` (invalid token) — bypassed the blocklist and was stored unchanged. On storage adapters that persist and serve the uploaded `Content-Type` (such as Amazon S3, Google Cloud Storage, or Azure Blob Storage), a browser cannot parse the malformed `Content-Type` and falls back to MIME-sniffing the file content; a file whose body begins with HTML markup is then rendered as HTML, executing any embedded script in the application's origin. This allows a user permitted to upload files to store content that executes as script against other users who open the file URL. The default GridFS storage adapter is not affected, as it recomputes the `
parse-server
source listedSEMVER: introduced 9.0.0; fixed 9.10.0-alpha.2
### Impact Parse Server's file upload validation uses the `fileUpload.fileExtensions` option (enabled by default with a blocklist) to reject files that browsers may render as active content, mitigating stored cross-site scripting (XSS). When an uploaded file's extension is not recognized by the `mime` package, Parse Server preserves the client-supplied `Content-Type` and passes it to the storage adapter. A malformed `Content-Type` that is not a valid `type/subtype` media type — for example `image` (no subtype), `image/` (empty subtype), or `image//svg+xml` (invalid token) — bypassed the blocklist and was stored unchanged. On storage adapters that persist and serve the uploaded `Content-Type` (such as Amazon S3, Google Cloud Storage, or Azure Blob Storage), a browser cannot parse the malformed `Content-Type` and falls back to MIME-sniffing the file content; a file whose body begins with HTML markup is then rendered as HTML, executing any embedded script in the application's origin. This allows a user permitted to upload files to store content that executes as script against other users who open the file URL. The default GridFS storage adapter is not affected, as it recomputes the `
parse-server
source listedSEMVER: introduced 0; fixed 8.6.84
### Impact Parse Server's file upload validation uses the `fileUpload.fileExtensions` option (enabled by default with a blocklist) to reject files that browsers may render as active content, mitigating stored cross-site scripting (XSS). When an uploaded file's extension is not recognized by the `mime` package, Parse Server preserves the client-supplied `Content-Type` and passes it to the storage adapter. A malformed `Content-Type` that is not a valid `type/subtype` media type — for example `image` (no subtype), `image/` (empty subtype), or `image//svg+xml` (invalid token) — bypassed the blocklist and was stored unchanged. On storage adapters that persist and serve the uploaded `Content-Type` (such as Amazon S3, Google Cloud Storage, or Azure Blob Storage), a browser cannot parse the malformed `Content-Type` and falls back to MIME-sniffing the file content; a file whose body begins with HTML markup is then rendered as HTML, executing any embedded script in the application's origin. This allows a user permitted to upload files to store content that executes as script against other users who open the file URL. The default GridFS storage adapter is not affected, as it recomputes the `
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
- vendor patch
The original advisory lists fixed boundaries 9.10.0-alpha.2 for parse-server. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
- vendor patch
The original advisory lists fixed boundaries 8.6.84 for parse-server. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-r899-h629-j84r ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- GHSA-r899-h629-j84r ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
- CVE-2026-61448 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 3 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.