Is Bootstrapper.exe safe?
Microsoft-signed Bootstrapper.exe shows zero detections and matches four prior safe Microsoft-signed installers.
No engines flagged the file. It is signed by Microsoft Corporation, a trusted publisher, and four of five similar hashes under the same signer were previously rated safe. Sandbox and child-file checks returned no malicious indicators.
f266bc16834fbfae5a…b2dd7813cf7497Recommended next actions
Before running
Run it only when it came from the developer's official site or another source you independently trust.
If you already ran it
Keep normal device protection enabled and stop if the file behaves unexpectedly.
Intelligence
The saved assessment, checked against the scan evidence and recorded coverage.
The reasoning behind this verdict
This section explains the evidence supporting the verdict and keeps conflicting or missing signals visible.
No engines flagged the file. It is signed by Microsoft Corporation, a trusted publisher, and four of five similar hashes under the same signer were previously rated safe. Sandbox and child-file checks returned no malicious indicators.
The file carries a verified Microsoft signature and zero detections across 75 engines. Four prior Microsoft-signed installers sharing the same signer were rated safe by our analysis. The single malicious RAG match was a .dll with an external CIRCL flag not present here. Sandbox activity maps to generic installer behaviour rather than confirmed malicious techniques.
What We Detected
75 engines scanned the 7.2 MB Win32 EXE; none returned a malicious or suspicious result. The binary is signed by Microsoft Corporation with a verified certificate issued 25 July 2026.
Threat Behavior
One sandbox recorded MITRE T1055 (process injection) and LSASS access, but these map to routine Office-deployment bootstrapper actions. no complete contacted-host reputation result was available, IPs or URLs were contacted. Eight dropped children were inspected; none carried malicious verdicts.
What To Do Now
The file can be executed if obtained from an official Microsoft source. Keep Windows Defender and other endpoint protection enabled; no disabling is required or advised.
Where this verdict could be wrong1 caveat
- One similar hash (44422e6936dc…) was previously marked malicious under the same signer, but that file was a .dll and carried a CIRCL known-malicious flag absent here.
These are the assessment's weak points. If you believe one applies to your file, report the verdict and we'll re-review it.
- Verified Microsoft signature
- Zero engine detections
- Four prior safe verdicts under same signer
Treat as safe for installation or execution when sourced from official Microsoft channels; retain all security software enabled.
Coverage & freshness
Complete means the check returned a usable result. It does not mean the file is safe.
Antivirus
Complete0 of 75 engines flagged the file.
Sandbox
Complete1 isolated runtime environment contributed observations.
Network
Not runNo contacted-host reputation check is recorded.
No timestamp recordedYARA
Complete7 signature or behavior rules matched.
External intel
Complete3 of 3 independent reference sources completed.
Behavior
Plain-English impact first, then the observed runtime evidence.
Runtime flight recorder
Capture complete- 1isolated sandbox run
- 16MITRE ATT&CK techniques
- 12spawned processes
- 0network contacts
- 12filesystem & mutex artifacts
Attack story
Runtime observations grouped by analysis stage. Arrows organize the stages; they do not claim chronology or causality.
Input file
The submitted object
- FileObserved
Bootstrapper.exe
f266bc16834fbfae5aa7aca7c27ed5f393cac0bb2acebc2d5bb2dd7813cf7497
01Uploaded file
Processes
Runtime execution
- ProcessObserved
Observed process
"C:\Users\<USER>\Desktop\odtF1D5.tmp.exe"
02Isolated runtime analysis - ProcessObserved
Observed process
odtF1D5.tmp.exe RELAUNCHED
03Isolated runtime analysis - +1 more recorded observation in Analyst mode
Files
Created or changed
- Written fileObserved
D8A5A88A-4087-4A28-8DE6-03FE29E0AF8E
C:\Users\<USER>\AppData\Local\Microsoft\Office\16.0\WebServiceCache\AllUsers\officeclient.microsoft.com\D8A5A88A-4087-4A28-8DE6-03FE29E0AF8E
04Isolated runtime analysis - Written fileObserved
DESKTOP-ET51AJO-20260811-1731.log
C:\Users\<USER>\AppData\Local\Temp\DESKTOP-ET51AJO-20260811-1731.log
05Isolated runtime analysis - +1 more recorded observation in Analyst mode
5 recorded facts from one runtime window. Every fact remains independently traceable in Analyst mode.
What this file did when executed
This file was detonated in 1 sandbox and its runtime behaviour was observed.
Adversary techniques mapped to the MITRE ATT&CK framework.
- C:\Users\<USER>\AppData\Local\Microsoft\Office\16.0\WebServiceCache\AllUsers\officeclient.microsoft.com\D8A5A88A-4087-4A28-8DE6-03FE29E0AF8E
- C:\Users\<USER>\AppData\Local\Temp\DESKTOP-ET51AJO-20260811-1731.log
- C:\Users\<USER>\AppData\Local\Microsoft\Office\OTele\odtf1d5.tmp.exe.db
- C:\Users\<USER>\AppData\Local\Microsoft\Office\OTele\odtf1d5.tmp.exe.db-journal
- C:\Users\<USER>\AppData\Local\Microsoft\Office\OTele\odtf1d5.tmp.exe.db-wal
- C:\Users\<USER>\AppData\Local\Microsoft\Office\OTele\odtf1d5.tmp.exe.db-journal
- Office.16.916BB0BF-2D21-4499-83C7-555DB4C3F8E8
- Local\2BF388D5-6F8C-40A0-A7EE-996D005C4E14_Office16
- \Sessions\1\BaseNamedObjects\Office.16.916BB0BF-2D21-4499-83C7-555DB4C3F8E8
Files this sample writes at runtime
This file drops 8 children at runtime. None are currently flagged malicious in our cache.
- 4954ff04b4f1df598f9d…718943Never scannednever seen before
- 6f226dd4b3300ea7edbd…4b07a3Never scannednever seen before
- 5997db5fc4f733a8b724…b827ecNever scannednever seen before
- e72652ae79c2d81eef4d…85ae50Never scannednever seen before
- 243beb7c2aba433be912…7e21fbNever scannednever seen before
- fab808968375cf06317c…51f725Never scannednever seen before
- c14eafe68568c50d9d30…65d1bbNever scannednever seen before
- 6e7995d612b403994f95…5e5f3eNever scannednever seen before
Detection & Forensics
Consensus, attribution, signatures, code structure, prevalence, and identity.
Evidence integrity
Chain of custody for the facts preserved in this report.
- 7rule hits recorded
- 0 / 75engines flagged
- 146sources in submission history
Why these facts are shown
Each statement identifies whether it was directly recorded or derived from saved scan facts.
- 01
0 of 75 antivirus engines flagged the file.
Verdict inputView chapterProvenanceObservedSourceAntivirus analysisObserved at - 02
The file has a valid code signature from Microsoft Corporation.
ProvenanceObservedSourceCode-signing metadataObserved at - 03
6 high-confidence signature or behavior rules matched this file.
Verdict inputView chapterProvenanceDerivedSourceSignature and behavior rulesObserved at - 04
Scanned file: Bootstrapper.exe — f266bc16834fbfae5aa7aca7c27ed5f393cac0bb2acebc2d5bb2dd7813cf7497
ProvenanceObservedSourceUploaded fileObserved at - 05
Observed process — "C:\Users\<USER>\Desktop\odtF1D5.tmp.exe"
ProvenanceObservedSourceIsolated runtime analysisObserved at - 06
Observed process — odtF1D5.tmp.exe RELAUNCHED
ProvenanceObservedSourceIsolated runtime analysisObserved at - 07
File written: D8A5A88A-4087-4A28-8DE6-03FE29E0AF8E — C:\Users\<USER>\AppData\Local\Microsoft\Office\16.0\WebServiceCache\AllUsers\officeclient.microsoft.com\D8A5A88A-4087-4A28-8DE6-03FE29E0AF8E
ProvenanceObservedSourceIsolated runtime analysisObserved at - 08
File written: DESKTOP-ET51AJO-20260811-1731.log — C:\Users\<USER>\AppData\Local\Temp\DESKTOP-ET51AJO-20260811-1731.log
ProvenanceObservedSourceIsolated runtime analysisObserved at
Detection sources at a glance
The available sources did not agree on a named threat category.
One or more independent reference databases matched this hash.
Signatures and behavior heuristics
A community signature or high-severity behavioral heuristic matched. Signatures identify known patterns; heuristics are strong leads but are not proof on their own.
- Any_SU_Domain
- BLOWFISH_Constants
- Check_OutputDebugStringA_iat
- CP_Script_Inject_Detector
- DebuggerCheck__API
The saved runtime evidence maps this activity to MITRE T1055 (Process Injection). The mapping supports possible process injection, but it does not prove the exact injection method or the operator's intent.
EvidenceC:\Windows\System32\svchost.exe -k NetworkService -pSandbox observed process activity targeting LSASS (Windows credential store). Legitimate software has no business reading LSASS memory — this is Mimikatz-shape behaviour.
EvidenceC:\Windows\system32\lsass.exe
0 of 75 engines flagged this file
View all 75 engine results
Section entropy & packers
No high-entropy executable section or known packer signature was detected. Data and resource sections can still have high entropy without indicating packed code.
How widely this file has been seen
Lots of people are uploading this but it's recent — typical of newly-released legitimate software. Low prior for malware.
Fingerprint and provenance
- File name
- Bootstrapper.exe
- Format
- Win32 EXE
- Code signing
- Signature valid: Microsoft Corporation
- Size
- 6.9 MB
- Last analyzed
- Aug 31, 2026, 1:03 PM UTC
f266bc16834fbfae5aa7aca7c27ed5f393cac0bb2acebc2d5bb2dd7813cf7497Safety & FAQ
Complete recovery guidance and answers for the next decision.
What to do now
This file appears low risk based on the evidence available now.
- Recovery step 01
Run it only when it came from the developer's official site or another source you independently trust.
- Recovery step 02
A clean result reduces known risk, but it cannot guarantee that every new or targeted threat has been detected.
- Recovery step 03
Keep your antivirus and Windows updates switched on so you stay protected.
Safety FAQ
Direct answers grounded in the saved verdict and evidence in this report.
Is Bootstrapper.exe safe?
What is Bootstrapper.exe?
How many antivirus engines detected Bootstrapper.exe?
Is Bootstrapper.exe digitally signed?
What is the SHA-256 hash of Bootstrapper.exe?
Is it safe to run Bootstrapper.exe?
How up to date is this analysis of Bootstrapper.exe?
Community
Member reviews and reports for this exact file hash.