There is no exhaustive list of material banned specifically in WhatsApp profile pictures, but there is an exhaustive list of crimes that § 140 StGB applies to:
Whoever
- rewards or
- approves of publicly, in a meeting or by disseminating material (section 11 (3)) in a manner which is suitable for causing a disturbance of the public peace
one of the unlawful acts referred to in section 138 (1) nos. 2 to 4 and no. 5 last alternative and in section 126 (1) or an unlawful act under section 176 (3), sections 176a and 176b, under section 177 (4) to (8) or section 178 after it has been committed or culpably attempted incurs a penalty of imprisonment for a term not exceeding three years or a fine.
In turn, sections 138 and 126 enumerate various crimes, whereas the other mentioned sections relate to (child) sexual abuse.
Section 138 (1) no. 5 lists:
murder under specific aggravating circumstances (section 211) or murder (section 212) or genocide (section 6 of the Code of Crimes against International Law) or a crime against humanity (section 7 of the Code of Crimes against International Law) or a war crime (section 8, 9, 10, 11 or 12 of the Code of Crimes against International Law) or a crime of aggression (section 13 of the Code of Crimes against International Law)
The last alternative is indeed a “crime of aggression” which is defined in particular as “the use of armed force by a State against the sovereignty, territorial integrity or political independence of another State, or in any other manner inconsistent with the Charter of the United Nations”.
In Germany, there is a clear consensus that Russia is waging a war of aggression against Ukraine. The “Z” symbol is used in a Russian context in support of this invasion. It is therefore understandable that a prosecutor has the reasonable suspicion that publicly posting a Russian flag with the Z symbol is public approval of this crime of aggression. Spiegel Online reported of 140 similar cases across Germany.
Thus, the photo could be real. Of course, the accused should not accept this invitation to talk to the police and instead get themselves a criminal defense attorney. A defense strategy would likely argue that the profile picture was not “suitable for causing a disturbance of the public peace” so that the conditions of § 140 StGB were not fulfilled. More realistically, the defendant would not contest a fine.